diff --git a/dotcom-rendering/eslint.config.mjs b/dotcom-rendering/eslint.config.mjs
index a5085a9a3b7..ec9e3fd6fcb 100644
--- a/dotcom-rendering/eslint.config.mjs
+++ b/dotcom-rendering/eslint.config.mjs
@@ -65,7 +65,11 @@ const rulesToEnforce = {
 
 export default defineConfig([
 	...guardian.configs.recommended,
-	...guardian.configs.jest,
+	...guardian.configs.jest.map((config) => ({
+		...config,
+		// Don't apply Jest globals to Node test files
+		ignores: [...(config.ignores ?? []), '**/*.node.test.ts'],
+	})),
 	...guardian.configs.react,
 	...guardian.configs.storybook,
 	// eslint-plugin-prettier/recommended should be the last item in the configuration array so that eslint-config-prettier has the opportunity to override other configs
diff --git a/dotcom-rendering/jest.config.js b/dotcom-rendering/jest.config.js
index 5257a547f9c..02fd5aad4d6 100644
--- a/dotcom-rendering/jest.config.js
+++ b/dotcom-rendering/jest.config.js
@@ -23,6 +23,7 @@ module.exports = {
 		'^.+\\.(mjs|js|ts|tsx)$': ['@swc/jest', swcConfig],
 	},
 	testMatch: ['**/*.test.+(ts|tsx|js)'],
+	testPathIgnorePatterns: ['\\.node\\.test\\.'],
 	setupFilesAfterEnv: ['<rootDir>/scripts/jest/setup.ts'],
 	moduleNameMapper: {
 		'^svgs/(.*)$': '<rootDir>/__mocks__/svgMock.tsx',
diff --git a/dotcom-rendering/package.json b/dotcom-rendering/package.json
index 2cfea960681..3fd983c6d01 100644
--- a/dotcom-rendering/package.json
+++ b/dotcom-rendering/package.json
@@ -10,6 +10,7 @@
 		"lint:stats": "pnpm lint --format node_modules/eslint-stats/byError.js",
 		"tsc": "tsc",
 		"test": "IMAGE_DIGEST=sha256:12345 jest --maxWorkers=50%",
+		"test:node": "IMAGE_DIGEST=sha256:12345 node --import=tsx --test \"src/**/*.node.test.ts\"",
 		"test:watch": "IMAGE_DIGEST=sha256:12345 jest --watch --maxWorkers=25%",
 		"test:ci": "IMAGE_DIGEST=sha256:12345 jest --runInBand",
 		"playwright:open": "playwright test --ui",
diff --git a/dotcom-rendering/src/components/ElectionTrackers/electionComponent.test.ts b/dotcom-rendering/src/components/ElectionTrackers/electionComponent.node.test.ts
similarity index 74%
rename from dotcom-rendering/src/components/ElectionTrackers/electionComponent.test.ts
rename to dotcom-rendering/src/components/ElectionTrackers/electionComponent.node.test.ts
index e076e41aa63..1cc4beec484 100644
--- a/dotcom-rendering/src/components/ElectionTrackers/electionComponent.test.ts
+++ b/dotcom-rendering/src/components/ElectionTrackers/electionComponent.node.test.ts
@@ -1,3 +1,4 @@
+import { it } from 'node:test';
 import { parse } from 'valibot';
 import { euParliament } from '../../../fixtures/manual/electionTrackers/euParliament';
 import { ukGeneralExitPoll } from '../../../fixtures/manual/electionTrackers/ukGeneralExitPoll';
@@ -7,26 +8,26 @@ import { usCongressEmpty } from '../../../fixtures/manual/electionTrackers/usCon
 import { usPresidential } from '../../../fixtures/manual/electionTrackers/usPresidential';
 import { ElectionComponents } from './electionComponent';
 
-it('validates US Congress data', () => {
+void it('validates US Congress data', () => {
 	parse(ElectionComponents, usCongressEmpty);
 });
 
-it('validates UK General data', () => {
+void it('validates UK General data', () => {
 	parse(ElectionComponents, ukGeneralFinal);
 });
 
-it('validates UK General Exit Poll data', () => {
+void it('validates UK General Exit Poll data', () => {
 	parse(ElectionComponents, ukGeneralExitPoll);
 });
 
-it('validates UK Local data', () => {
+void it('validates UK Local data', () => {
 	parse(ElectionComponents, ukLocal);
 });
 
-it('validates US Presidential data', () => {
+void it('validates US Presidential data', () => {
 	parse(ElectionComponents, usPresidential);
 });
 
-it('validates EU Parliament data', () => {
+void it('validates EU Parliament data', () => {
 	parse(ElectionComponents, euParliament);
 });
diff --git a/dotcom-rendering/src/cricketMatch.test.ts b/dotcom-rendering/src/cricketMatch.node.test.ts
similarity index 61%
rename from dotcom-rendering/src/cricketMatch.test.ts
rename to dotcom-rendering/src/cricketMatch.node.test.ts
index 3391ddd6ff8..2c4b45ad2e7 100644
--- a/dotcom-rendering/src/cricketMatch.test.ts
+++ b/dotcom-rendering/src/cricketMatch.node.test.ts
@@ -1,14 +1,16 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import { liveMatch, resultMatch } from '../fixtures/manual/cricketMatch';
 import { parseCricketMatch } from './cricketMatch';
 
-describe('parseCricketMatchV2', () => {
-	it('parses a winner result cricket match correctly', () => {
+void describe('parseCricketMatchV2', () => {
+	void it('parses a winner result cricket match correctly', () => {
 		const result = parseCricketMatch(resultMatch).getOrThrow(
 			'Expected parsing cricket match to succeed',
 		);
 
-		expect(result.kind).toEqual('Result');
-		expect(result.result).toEqual({
+		assert.equal(result.kind, 'Result');
+		assert.deepEqual(result.result, {
 			type: 'home-win',
 			description: 'England win by 115 runs',
 			winner: {
@@ -17,32 +19,35 @@ describe('parseCricketMatchV2', () => {
 				margin: 115,
 			},
 		});
-		expect(result.matchDate).toEqual(new Date('2026-06-17T10:00:00.000Z'));
+		assert.deepEqual(
+			result.matchDate,
+			new Date('2026-06-17T10:00:00.000Z'),
+		);
 	});
 
-	it('parses a cricket match in pre-match status', () => {
+	void it('parses a cricket match in pre-match status', () => {
 		const result = parseCricketMatch({
 			...liveMatch,
 			result: 'pre-match',
 			fullResult: undefined,
 		}).getOrThrow('Expected parsing cricket match to succeed');
 
-		expect(result.kind).toEqual('Fixture');
-		expect(result.result).toEqual(undefined);
+		assert.equal(result.kind, 'Fixture');
+		assert.equal(result.result, undefined);
 	});
 
-	it('parses a cricket match in in-play status', () => {
+	void it('parses a cricket match in in-play status', () => {
 		const result = parseCricketMatch({
 			...liveMatch,
 			result: 'in-play',
 			fullResult: undefined,
 		}).getOrThrow('Expected parsing cricket match to succeed');
 
-		expect(result.kind).toEqual('Live');
-		expect(result.result).toEqual(undefined);
+		assert.equal(result.kind, 'Live');
+		assert.equal(result.result, undefined);
 	});
 
-	it('parses an abandoned cricket match correctly', () => {
+	void it('parses an abandoned cricket match correctly', () => {
 		const result = parseCricketMatch({
 			...liveMatch,
 			fullResult: {
@@ -52,14 +57,13 @@ describe('parseCricketMatchV2', () => {
 			},
 		}).getOrThrow('Expected parsing cricket match to succeed');
 
-		expect(result.result).toEqual({
+		assert.deepEqual(result.result, {
 			type: 'abandoned',
 			description: 'Match abandoned due to rain',
-			winner: undefined,
 		});
 	});
 
-	it('parses a cricket match with no winner', () => {
+	void it('parses a cricket match with no winner', () => {
 		const result = parseCricketMatch({
 			...liveMatch,
 			fullResult: {
@@ -69,10 +73,9 @@ describe('parseCricketMatchV2', () => {
 			},
 		}).getOrThrow('Expected parsing cricket match to succeed');
 
-		expect(result.result).toEqual({
+		assert.deepEqual(result.result, {
 			type: 'no-result',
 			description: 'No result',
-			winner: undefined,
 		});
 	});
 });
diff --git a/dotcom-rendering/src/footballMatches.test.ts b/dotcom-rendering/src/footballMatches.node.test.ts
similarity index 72%
rename from dotcom-rendering/src/footballMatches.test.ts
rename to dotcom-rendering/src/footballMatches.node.test.ts
index 35faf608661..cbdee653b5c 100644
--- a/dotcom-rendering/src/footballMatches.test.ts
+++ b/dotcom-rendering/src/footballMatches.node.test.ts
@@ -1,3 +1,5 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import { footballData } from '../fixtures/generated/football-live';
 import {
 	emptyMatches,
@@ -25,25 +27,25 @@ const withMatches = (
 		})),
 	}));
 
-describe('footballMatches', () => {
-	it('should parse match fixtures correctly', () => {
+void describe('footballMatches', () => {
+	void it('should parse match fixtures correctly', () => {
 		const result = parse(footballData.matchesList).getOrThrow(
 			'Expected football match parsing to succeed',
 		);
 
-		expect(result.length).toBe(1);
+		assert.equal(result.length, 1);
 
 		const day = result[0];
-		expect(day?.dateISOString).toBe('2025-04-28T00:00:00.000Z');
-		expect(day?.competitions.length).toBe(2);
+		assert.equal(day?.dateISOString, '2025-04-28T00:00:00.000Z');
+		assert.equal(day?.competitions.length, 2);
 
 		const competition = day?.competitions[0];
-		expect(competition?.name).toBe('Serie A');
-		expect(competition?.matches[0]?.kind).toBe('Fixture');
-		expect(competition?.tag).toBe('football/serieafootball');
+		assert.equal(competition?.name, 'Serie A');
+		assert.equal(competition?.matches[0]?.kind, 'Fixture');
+		assert.equal(competition?.tag, 'football/serieafootball');
 	});
 
-	it('should return an error when football days have invalid dates', () => {
+	void it('should return an error when football days have invalid dates', () => {
 		const invalidDate: FEMatchByDateAndCompetition[] = emptyMatches.map(
 			(day) => ({
 				...day,
@@ -55,10 +57,10 @@ describe('footballMatches', () => {
 			'Expected football match parsing to fail',
 		);
 
-		expect(result.kind).toBe('FootballDayInvalidDate');
+		assert.equal(result.kind, 'FootballDayInvalidDate');
 	});
 
-	it('should return an error when football matches have an invalid date', () => {
+	void it('should return an error when football matches have an invalid date', () => {
 		const invalidMatchResult: FEMatchByDateAndCompetition[] = withMatches([
 			matchFixture,
 			{ ...matchResult, date: '' },
@@ -85,24 +87,24 @@ describe('footballMatches', () => {
 			'Expected football match parsing to fail',
 		);
 
-		expect(resultOne.kind).toBe('FootballMatchInvalidDate');
-		expect(resultTwo.kind).toBe('FootballMatchInvalidDate');
+		assert.equal(resultOne.kind, 'FootballMatchInvalidDate');
+		assert.equal(resultTwo.kind, 'FootballMatchInvalidDate');
 
 		if (resultThree.kind !== 'InvalidMatchDay') {
 			throw new Error('Expected an invalid match day error');
 		}
 
-		expect(resultThree.errors[0]!.kind).toBe('FootballMatchInvalidDate');
+		assert.equal(resultThree.errors[0]!.kind, 'FootballMatchInvalidDate');
 	});
 
-	it('should return an error when it receives a live match', () => {
+	void it('should return an error when it receives a live match', () => {
 		const result = parse(withMatches([liveMatch])).getErrorOrThrow(
 			'Expected football match parsing to fail',
 		);
 
-		expect(result.kind).toBe('UnexpectedLiveMatch');
+		assert.equal(result.kind, 'UnexpectedLiveMatch');
 	});
-	it('should return a clean team name', () => {
+	void it('should return a clean team name', () => {
 		const matchesListWithTeamName = (teamName: string): FEResult => {
 			return {
 				...matchResult,
@@ -136,10 +138,10 @@ describe('footballMatches', () => {
 				throw new Error('Expected Result');
 			}
 
-			expect(match.homeTeam.name).toBe(cleanName);
+			assert.equal(match.homeTeam.name, cleanName);
 		}
 	});
-	it('should replace known live match status with our status', () => {
+	void it('should replace known live match status with our status', () => {
 		const matchDay = parse(
 			withMatches([matchDayLiveSecondHalf]),
 		).getOrThrow('Expected football live match parsing to succeed');
@@ -149,9 +151,9 @@ describe('footballMatches', () => {
 			throw new Error('Expected live match');
 		}
 
-		expect(match.status).toBe('2nd');
+		assert.equal(match.status, '2nd');
 	});
-	it('should replace unknown live match status with first two characters', () => {
+	void it('should replace unknown live match status with first two characters', () => {
 		const matchDayLiveUnknownStatus = {
 			...matchDayLiveSecondHalf,
 			matchStatus: 'Something odd',
@@ -166,6 +168,6 @@ describe('footballMatches', () => {
 			throw new Error('Expected live match');
 		}
 
-		expect(match.status).toBe('So');
+		assert.equal(match.status, 'So');
 	});
 });
diff --git a/dotcom-rendering/src/lib/acquisitions.test.ts b/dotcom-rendering/src/lib/acquisitions.node.test.ts
similarity index 82%
rename from dotcom-rendering/src/lib/acquisitions.test.ts
rename to dotcom-rendering/src/lib/acquisitions.node.test.ts
index c48945d3eda..f178aae651c 100644
--- a/dotcom-rendering/src/lib/acquisitions.test.ts
+++ b/dotcom-rendering/src/lib/acquisitions.node.test.ts
@@ -1,7 +1,9 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import { addTrackingCodesToUrl } from './acquisitions';
 
-describe('acquisitions', () => {
-	it('should addTrackingCodesToUrl', () => {
+void describe('acquisitions', () => {
+	void it('should addTrackingCodesToUrl', () => {
 		const result = addTrackingCodesToUrl({
 			base: `https://support.theguardian.com/contribute`,
 			componentType: 'ACQUISITIONS_HEADER',
@@ -15,7 +17,8 @@ describe('acquisitions', () => {
 			referrerUrl: 'https://theguardian.com/uk',
 		});
 
-		expect(result).toEqual(
+		assert.equal(
+			result,
 			'https://support.theguardian.com/contribute?REFPVID=abcdefg&INTCMP=header_support&acquisitionData=%7B%22source%22%3A%22GUARDIAN_WEB%22%2C%22componentId%22%3A%22header_support%22%2C%22componentType%22%3A%22ACQUISITIONS_HEADER%22%2C%22campaignCode%22%3A%22header_support%22%2C%22abTest%22%3A%7B%22name%22%3A%22testName%22%2C%22variant%22%3A%22variantName%22%7D%2C%22referrerPageviewId%22%3A%22abcdefg%22%2C%22referrerUrl%22%3A%22https%3A%2F%2Ftheguardian.com%2Fuk%22%7D',
 		);
 	});
diff --git a/dotcom-rendering/src/lib/ad-targeting.test.ts b/dotcom-rendering/src/lib/ad-targeting.node.test.ts
similarity index 81%
rename from dotcom-rendering/src/lib/ad-targeting.test.ts
rename to dotcom-rendering/src/lib/ad-targeting.node.test.ts
index 88da2cf0099..d4f6204fe42 100644
--- a/dotcom-rendering/src/lib/ad-targeting.test.ts
+++ b/dotcom-rendering/src/lib/ad-targeting.node.test.ts
@@ -1,3 +1,5 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import { buildAdTargeting } from './ad-targeting';
 
 const sharedAdTargeting = {
@@ -12,7 +14,7 @@ const sharedAdTargeting = {
 	url: '/money/2017/mar/10/ministers-to-criminalise-use-of-ticket-tout-harvesting-software',
 };
 
-describe('buildAdTargeting', () => {
+void describe('buildAdTargeting', () => {
 	const expectedAdTargeting = {
 		adUnit: '/59666047/theguardian.com/money/article/ng',
 		customParams: {
@@ -38,8 +40,8 @@ describe('buildAdTargeting', () => {
 		},
 	};
 
-	it('builds adTargeting correctly', () => {
-		expect(
+	void it('builds adTargeting correctly', () => {
+		assert.deepEqual(
 			buildAdTargeting({
 				isAdFreeUser: false,
 				isSensitive: false,
@@ -48,6 +50,7 @@ describe('buildAdTargeting', () => {
 				sharedAdTargeting,
 				adUnit: '/59666047/theguardian.com/money/article/ng',
 			}),
-		).toEqual(expectedAdTargeting);
+			expectedAdTargeting,
+		);
 	});
 });
diff --git a/dotcom-rendering/src/lib/affiliateLinksUtils.test.ts b/dotcom-rendering/src/lib/affiliateLinksUtils.node.test.ts
similarity index 66%
rename from dotcom-rendering/src/lib/affiliateLinksUtils.test.ts
rename to dotcom-rendering/src/lib/affiliateLinksUtils.node.test.ts
index afbfd29bb00..25a786c1fb7 100644
--- a/dotcom-rendering/src/lib/affiliateLinksUtils.test.ts
+++ b/dotcom-rendering/src/lib/affiliateLinksUtils.node.test.ts
@@ -1,29 +1,31 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import {
 	buildMergedAbTestString,
 	buildXcustParamForAffiliateLink,
 	extractAbTestParticipationFromUrl,
 } from './affiliateLinksUtils';
 
-describe('extractAbTestParticipationFromUrl', () => {
-	it('extracts AB test participations from xcust', () => {
+void describe('extractAbTestParticipationFromUrl', () => {
+	void it('extracts AB test participations from xcust', () => {
 		const url =
 			'https://go.skimresources.com/?id=114047X1572903&url=https%3A%2F%2Fwww.argos.co.uk%2Fproduct%2F8112969&sref=https://www.theguardian.com/thefilter/2024/nov/21/best-coffee-machines&xcust=referrer%7Cwww.theguardian.com%7CaccountId%7C114047X1572903%7CabTestParticipations%7Cthefilter-at-a-glance-redesign-v2%3Acarousel%7CcomponentId%7Ccarousel-card';
 
-		expect(extractAbTestParticipationFromUrl(url)).toEqual({
+		assert.deepEqual(extractAbTestParticipationFromUrl(url), {
 			'thefilter-at-a-glance-redesign-v2': 'carousel',
 		});
 	});
 
-	it('returns empty object when xcust has no AB test section', () => {
+	void it('returns empty object when xcust has no AB test section', () => {
 		const url =
 			'https://go.skimresources.com/?id=114047X1572903&url=https%3A%2F%2Fwww.argos.co.uk%2Fproduct%2F8112969&xcust=referrer%7Cwww.theguardian.com%7CaccountId%7C114047X1572903%7CcomponentId%7Ccarousel-card';
 
-		expect(extractAbTestParticipationFromUrl(url)).toEqual({});
+		assert.deepEqual(extractAbTestParticipationFromUrl(url), {});
 	});
 });
 
-describe('buildXcustValueForAffiliateLink', () => {
-	it('returns xcust value for skimlinks URLs', () => {
+void describe('buildXcustValueForAffiliateLink', () => {
+	void it('returns xcust value for skimlinks URLs', () => {
 		const xcustResult = buildXcustParamForAffiliateLink({
 			url: new URL(
 				'https://go.skimresources.com/?id=1234X9876&url=https%3A%2F%2Fwww.theguardian.com%2Fuk',
@@ -34,12 +36,13 @@ describe('buildXcustValueForAffiliateLink', () => {
 			xcustComponentId: null,
 		});
 
-		expect(xcustResult).toBe(
+		assert.equal(
+			xcustResult,
 			'referrer|www.theguardian.com|accountId|1234X9876',
 		);
 	});
 
-	it('includes optional xcust values when provided', () => {
+	void it('includes optional xcust values when provided', () => {
 		const xcustResult = buildXcustParamForAffiliateLink({
 			url: new URL(
 				'https://go.skimresources.com/?id=1111&url=https%3A%2F%2Fwww.theguardian.com%2Fus-news',
@@ -50,12 +53,13 @@ describe('buildXcustValueForAffiliateLink', () => {
 			xcustComponentId: 'related-content',
 		});
 
-		expect(xcustResult).toBe(
+		assert.equal(
+			xcustResult,
 			'referrer|www.theguardian.com|accountId|1111|abTestParticipations|abTest1:variantA|utm_medium|cpc|utm_campaign|summer|componentId|related-content',
 		);
 	});
 
-	it('merges existing and incoming AB test participations', () => {
+	void it('merges existing and incoming AB test participations', () => {
 		const xcustResult = buildXcustParamForAffiliateLink({
 			url: new URL(
 				'https://go.skimresources.com/?id=1111&url=https%3A%2F%2Fwww.theguardian.com%2Fus-news&xcust=referrer%7Cwww.theguardian.com%7CaccountId%7C1111%7CabTestParticipations%7CexistingTest%3Acontrol%2CabTest1%3AoldVariant',
@@ -66,14 +70,14 @@ describe('buildXcustValueForAffiliateLink', () => {
 			xcustComponentId: null,
 		});
 
-		expect(xcustResult).toContain('|abTestParticipations|');
-		expect(xcustResult).toContain('existingTest:control');
-		expect(xcustResult).toContain('newTest:variantB');
-		expect(xcustResult).toContain('abTest1:oldVariant');
-		expect(xcustResult).not.toContain('abTest1:variantA');
+		assert(xcustResult.includes('|abTestParticipations|'));
+		assert(xcustResult.includes('existingTest:control'));
+		assert(xcustResult.includes('newTest:variantB'));
+		assert(xcustResult.includes('abTest1:oldVariant'));
+		assert(!xcustResult.includes('abTest1:variantA'));
 	});
 
-	it('preserves existing AB participations when url already has xcust', () => {
+	void it('preserves existing AB participations when url already has xcust', () => {
 		const xcustResult = buildXcustParamForAffiliateLink({
 			url: new URL(
 				'https://go.skimresources.com/?id=1111&url=https%3A%2F%2Fwww.theguardian.com%2Fus-news&xcust=referrer%7Cold.example%7CaccountId%7C1111%7CabTestParticipations%7ColdTest%3AoldVariant',
@@ -84,20 +88,20 @@ describe('buildXcustValueForAffiliateLink', () => {
 			xcustComponentId: null,
 		});
 
-		expect(xcustResult).toContain(
-			'referrer|www.theguardian.com|accountId|1111',
+		assert(
+			xcustResult.includes('referrer|www.theguardian.com|accountId|1111'),
 		);
-		expect(xcustResult).toContain('newTest:newVariant');
-		expect(xcustResult).toContain('oldTest:oldVariant');
+		assert(xcustResult.includes('newTest:newVariant'));
+		assert(xcustResult.includes('oldTest:oldVariant'));
 	});
 });
 
-describe('buildMergedAbTestString', () => {
-	it('returns incoming AB test string when URL has no existing participations', () => {
+void describe('buildMergedAbTestString', () => {
+	void it('returns incoming AB test string when URL has no existing participations', () => {
 		const url =
 			'https://go.skimresources.com/?id=1111&url=https%3A%2F%2Fwww.theguardian.com%2Fus-news';
 
-		expect(
+		assert.equal(
 			buildMergedAbTestString({
 				url,
 				abTestParticipations: {
@@ -105,20 +109,22 @@ describe('buildMergedAbTestString', () => {
 					abTest2: 'variantB',
 				},
 			}),
-		).toBe('abTest1:variantA,abTest2:variantB');
+			'abTest1:variantA,abTest2:variantB',
+		);
 	});
 
-	it('keeps existing URL values when keys collide', () => {
+	void it('keeps existing URL values when keys collide', () => {
 		const url =
 			'https://go.skimresources.com/?id=1111&url=https%3A%2F%2Fwww.theguardian.com%2Fus-news&xcust=referrer%7Cwww.theguardian.com%7CaccountId%7C1111%7CabTestParticipations%7ColdTest%3AoldVariant';
 
-		expect(
+		assert.equal(
 			buildMergedAbTestString({
 				url,
 				abTestParticipations: {
 					newTest: 'newVariant',
 				},
 			}),
-		).toBe('newTest:newVariant,oldTest:oldVariant');
+			'newTest:newVariant,oldTest:oldVariant',
+		);
 	});
 });
diff --git a/dotcom-rendering/src/lib/age-warning.node.test.ts b/dotcom-rendering/src/lib/age-warning.node.test.ts
new file mode 100644
index 00000000000..e3d299e2bac
--- /dev/null
+++ b/dotcom-rendering/src/lib/age-warning.node.test.ts
@@ -0,0 +1,57 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+import type { TagType } from '../types/tag';
+import { getAgeWarning } from './age-warning';
+
+void describe('getAgeWarning', () => {
+	const infoTag: TagType = {
+		id: 'info/info',
+		type: 'info',
+		title: 'info',
+	};
+	const studentsTag: TagType = {
+		id: 'education/students',
+		type: 'topic',
+		title: 'info',
+	};
+
+	const today = new Date();
+	const oneMonthOld = new Date(
+		new Date().setDate(today.getDate() - 31),
+	).toDateString();
+	const twoMonthsOld = new Date(
+		new Date().setDate(today.getDate() - 65),
+	).toDateString();
+	const oneYearOld = new Date(
+		new Date().setDate(today.getDate() - 370),
+	).toDateString();
+	const twoYearsOld = new Date(
+		new Date().setDate(today.getDate() - 750),
+	).toDateString();
+
+	void it('shows age warning when publication date is more than 1 month ago', () => {
+		assert.equal(getAgeWarning([studentsTag], oneMonthOld), '1 month old');
+	});
+
+	void it('shows age warning when publication date is more than 2 months ago', () => {
+		assert.equal(
+			getAgeWarning([studentsTag], twoMonthsOld),
+			'2 months old',
+		);
+	});
+
+	void it('shows age warning when publication date is more than 1 year ago', () => {
+		assert.equal(getAgeWarning([studentsTag], oneYearOld), '1 year old');
+	});
+
+	void it('shows age warning when publication date is more than 2 years ago', () => {
+		assert.equal(getAgeWarning([studentsTag], twoYearsOld), '2 years old');
+	});
+
+	void it('is undefined if one of the tags is excluded from age warning', () => {
+		assert.equal(
+			getAgeWarning([studentsTag, infoTag], oneMonthOld),
+			undefined,
+		);
+	});
+});
diff --git a/dotcom-rendering/src/lib/age-warning.test.ts b/dotcom-rendering/src/lib/age-warning.test.ts
deleted file mode 100644
index 277532da78b..00000000000
--- a/dotcom-rendering/src/lib/age-warning.test.ts
+++ /dev/null
@@ -1,54 +0,0 @@
-import type { TagType } from '../types/tag';
-import { getAgeWarning } from './age-warning';
-
-describe('getAgeWarning', () => {
-	const infoTag: TagType = {
-		id: 'info/info',
-		type: 'info',
-		title: 'info',
-	};
-	const studentsTag: TagType = {
-		id: 'education/students',
-		type: 'topic',
-		title: 'info',
-	};
-
-	const today = new Date();
-	const oneMonthOld = new Date(
-		new Date().setDate(today.getDate() - 31),
-	).toDateString();
-	const twoMonthsOld = new Date(
-		new Date().setDate(today.getDate() - 65),
-	).toDateString();
-	const oneYearOld = new Date(
-		new Date().setDate(today.getDate() - 370),
-	).toDateString();
-	const twoYearsOld = new Date(
-		new Date().setDate(today.getDate() - 750),
-	).toDateString();
-
-	it('shows age warning when publication date is more than 1 month ago', () => {
-		const testTags = [studentsTag];
-		expect(getAgeWarning(testTags, oneMonthOld)).toEqual('1 month old');
-	});
-
-	it('shows age warning when publication date is more than 2 months ago', () => {
-		const testTags = [studentsTag];
-		expect(getAgeWarning(testTags, twoMonthsOld)).toEqual('2 months old');
-	});
-
-	it('shows age warning when publication date is more than 1 year ago', () => {
-		const testTags = [studentsTag];
-		expect(getAgeWarning(testTags, oneYearOld)).toEqual('1 year old');
-	});
-
-	it('shows age warning when publication date is more than 2 years ago', () => {
-		const testTags = [studentsTag];
-		expect(getAgeWarning(testTags, twoYearsOld)).toEqual('2 years old');
-	});
-
-	it('is undefined if one of the tags is excluded from age warning', () => {
-		const testTags = [studentsTag, infoTag];
-		expect(getAgeWarning(testTags, oneMonthOld)).toEqual(undefined);
-	});
-});
diff --git a/dotcom-rendering/src/lib/alternate-lang-links.test.ts b/dotcom-rendering/src/lib/alternate-lang-links.node.test.ts
similarity index 61%
rename from dotcom-rendering/src/lib/alternate-lang-links.test.ts
rename to dotcom-rendering/src/lib/alternate-lang-links.node.test.ts
index e23db28bb89..69371d1311d 100644
--- a/dotcom-rendering/src/lib/alternate-lang-links.test.ts
+++ b/dotcom-rendering/src/lib/alternate-lang-links.node.test.ts
@@ -1,3 +1,5 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import { generateAlternateLangLinks } from './alternate-lang-links';
 import { editionalisedPages, editionList } from './edition';
 
@@ -11,31 +13,24 @@ const everyEditionWithNoLangLocale = editionList.filter(
 
 const everyEditionWithEditionalisedPages = editionList
 	.filter((edition) => edition.hasEditionalisedPages)
-	.map((edition) =>
+	.flatMap((edition) =>
 		editionalisedPages.map((page) => `${edition.pageId}/${page}`),
-	)
-	.flat();
+	);
 
-// This is an invalid combination e.g. europe/travel
 const everyEditionWithNoEditionalisedPages = editionList
 	.filter((edition) => !edition.hasEditionalisedPages)
-	.map((edition) =>
+	.flatMap((edition) =>
 		editionalisedPages.map((page) => `${edition.pageId}/${page}`),
-	)
-	.flat();
+	);
 
-describe('alternate lang links', () => {
-	it('generate hreflang links for network fronts with a lang locale', () => {
-		const langLinksForEditionsWithLangLocale =
-			everyEditionWithLangLocale.map((edition) => {
-				return generateAlternateLangLinks(
-					'https://www.theguardian.com',
-					edition.pageId,
-				);
-			});
-		for (const langLinks of langLinksForEditionsWithLangLocale) {
-			expect(langLinks.length).toBe(5);
-			expect(langLinks).toEqual([
+void describe('alternate lang links', () => {
+	void it('generate hreflang links for network fronts with a lang locale', () => {
+		for (const edition of everyEditionWithLangLocale) {
+			const langLinks = generateAlternateLangLinks(
+				'https://www.theguardian.com',
+				edition.pageId,
+			);
+			assert.deepEqual(langLinks, [
 				'<link rel="alternate" href="https://www.theguardian.com/uk" hreflang="en-GB" />',
 				'<link rel="alternate" href="https://www.theguardian.com/us" hreflang="en-US" />',
 				'<link rel="alternate" href="https://www.theguardian.com/au" hreflang="en-AU" />',
@@ -44,43 +39,47 @@ describe('alternate lang links', () => {
 			]);
 		}
 	});
-	it('do NOT generate hreflang links for network fronts with NO lang locale', () => {
-		const langLinksForEditionsWithNoLangLocale =
-			everyEditionWithNoLangLocale.map((edition) => {
-				return generateAlternateLangLinks(
+
+	void it('do NOT generate hreflang links for network fronts with NO lang locale', () => {
+		for (const edition of everyEditionWithNoLangLocale) {
+			assert.deepEqual(
+				generateAlternateLangLinks(
 					'https://www.theguardian.com',
 					edition.pageId,
-				);
-			});
-		for (const langLinks of langLinksForEditionsWithNoLangLocale) {
-			expect(langLinks.length).toBe(0);
+				),
+				[],
+			);
 		}
 	});
-	it('generate hreflang links for editionalised pages', () => {
+
+	void it('generate hreflang links for editionalised pages', () => {
 		for (const pageId of everyEditionWithEditionalisedPages) {
 			const langLinks = generateAlternateLangLinks(
 				'https://www.theguardian.com',
 				pageId,
 			);
 			const pageIdSuffix = pageId.split('/')[1] ?? '';
-			expect(langLinks.length).toBe(3);
-			expect(langLinks).toEqual([
+			assert.deepEqual(langLinks, [
 				`<link rel="alternate" href="https://www.theguardian.com/uk/${pageIdSuffix}" hreflang="en-GB" />`,
 				`<link rel="alternate" href="https://www.theguardian.com/us/${pageIdSuffix}" hreflang="en-US" />`,
 				`<link rel="alternate" href="https://www.theguardian.com/au/${pageIdSuffix}" hreflang="en-AU" />`,
 			]);
 		}
 	});
-	it('do NOT generate hreflang links for editions with NO editionalised pages', () => {
+
+	void it('do NOT generate hreflang links for editions with NO editionalised pages', () => {
 		for (const pageId of everyEditionWithNoEditionalisedPages) {
-			const langLinks = generateAlternateLangLinks(
-				'https://www.theguardian.com',
-				pageId,
+			assert.deepEqual(
+				generateAlternateLangLinks(
+					'https://www.theguardian.com',
+					pageId,
+				),
+				[],
 			);
-			expect(langLinks.length).toBe(0);
 		}
 	});
-	it('do NOT generate hreflang links for NON editionalised pages', () => {
+
+	void it('do NOT generate hreflang links for NON editionalised pages', () => {
 		const pageIdsNotEditionalisedPages = [
 			'uk/something',
 			'us/something',
@@ -89,11 +88,13 @@ describe('alternate lang links', () => {
 			'uk/business/something',
 		];
 		for (const pageId of pageIdsNotEditionalisedPages) {
-			const langLinks = generateAlternateLangLinks(
-				'https://www.theguardian.com',
-				pageId,
+			assert.deepEqual(
+				generateAlternateLangLinks(
+					'https://www.theguardian.com',
+					pageId,
+				),
+				[],
 			);
-			expect(langLinks.length).toBe(0);
 		}
 	});
 });
diff --git a/dotcom-rendering/src/lib/articleMeta.node.test.ts b/dotcom-rendering/src/lib/articleMeta.node.test.ts
new file mode 100644
index 00000000000..1d7a38dfbfe
--- /dev/null
+++ b/dotcom-rendering/src/lib/articleMeta.node.test.ts
@@ -0,0 +1,61 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+import { ArticleDesign, ArticleDisplay, Pillar } from './articleFormat';
+import { shouldShowContributor } from './articleMeta';
+
+void describe('shouldShowContributor', () => {
+	const standardFormat = {
+		theme: Pillar.News,
+		design: ArticleDesign.Standard,
+		display: ArticleDisplay.Standard,
+	};
+	const standardComment = {
+		...standardFormat,
+		design: ArticleDesign.Comment,
+	};
+	const showcaseStandard = {
+		...standardFormat,
+		display: ArticleDisplay.Showcase,
+	};
+	const showcaseComment = {
+		...showcaseStandard,
+		design: ArticleDesign.Comment,
+	};
+	const numberedList = {
+		...standardFormat,
+		display: ArticleDisplay.NumberedList,
+	};
+
+	const immersive = {
+		...standardFormat,
+		display: ArticleDisplay.Immersive,
+	};
+
+	void it('should return true if Standard display and Standard design', () => {
+		assert.equal(shouldShowContributor(standardFormat), true);
+	});
+
+	void it('should return false if Standard display and Comment design', () => {
+		assert.equal(shouldShowContributor(standardComment), false);
+	});
+
+	void it('should return true if Showcase display and Standard design', () => {
+		assert.equal(shouldShowContributor(showcaseStandard), true);
+	});
+
+	void it('should return false if Showcase display and Comment design', () => {
+		assert.equal(shouldShowContributor(showcaseComment), false);
+	});
+
+	void it('should return true if Numbered list display', () => {
+		assert.equal(shouldShowContributor(numberedList), true);
+	});
+
+	void it('should return false if Immersive display', () => {
+		assert.equal(shouldShowContributor(immersive), false);
+	});
+
+	void it('should return true if Immersive display uses the new grid', () => {
+		assert.equal(shouldShowContributor(immersive, true), true);
+	});
+});
diff --git a/dotcom-rendering/src/lib/articleMeta.test.ts b/dotcom-rendering/src/lib/articleMeta.test.ts
deleted file mode 100644
index 2955e6918c7..00000000000
--- a/dotcom-rendering/src/lib/articleMeta.test.ts
+++ /dev/null
@@ -1,59 +0,0 @@
-import { ArticleDesign, ArticleDisplay, Pillar } from './articleFormat';
-import { shouldShowContributor } from './articleMeta';
-
-describe('shouldShowContributor', () => {
-	const standardFormat = {
-		theme: Pillar.News,
-		design: ArticleDesign.Standard,
-		display: ArticleDisplay.Standard,
-	};
-	const standardComment = {
-		...standardFormat,
-		design: ArticleDesign.Comment,
-	};
-	const showcaseStandard = {
-		...standardFormat,
-		display: ArticleDisplay.Showcase,
-	};
-	const showcaseComment = {
-		...showcaseStandard,
-		design: ArticleDesign.Comment,
-	};
-	const numberedList = {
-		...standardFormat,
-		display: ArticleDisplay.NumberedList,
-	};
-
-	const immersive = {
-		...standardFormat,
-		display: ArticleDisplay.Immersive,
-	};
-
-	it('should return true if Standard display and Standard design', () => {
-		expect(shouldShowContributor(standardFormat)).toBe(true);
-	});
-
-	it('should return false if Standard display and Comment design', () => {
-		expect(shouldShowContributor(standardComment)).toBe(false);
-	});
-
-	it('should return true if Showcase display and Standard design', () => {
-		expect(shouldShowContributor(showcaseStandard)).toBe(true);
-	});
-
-	it('should return false if Showcase display and Comment design', () => {
-		expect(shouldShowContributor(showcaseComment)).toBe(false);
-	});
-
-	it('should return true if Numbered list display', () => {
-		expect(shouldShowContributor(numberedList)).toBe(true);
-	});
-
-	it('should return false if Immersive display', () => {
-		expect(shouldShowContributor(immersive)).toBe(false);
-	});
-
-	it('should return true if Immersive display uses the new grid', () => {
-		expect(shouldShowContributor(immersive, true)).toBe(true);
-	});
-});
diff --git a/dotcom-rendering/src/lib/branding.test.ts b/dotcom-rendering/src/lib/branding.node.test.ts
similarity index 84%
rename from dotcom-rendering/src/lib/branding.test.ts
rename to dotcom-rendering/src/lib/branding.node.test.ts
index 498c28b6f89..5b229e3c9d7 100644
--- a/dotcom-rendering/src/lib/branding.test.ts
+++ b/dotcom-rendering/src/lib/branding.node.test.ts
@@ -1,11 +1,13 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import type { Branding } from '../types/branding';
 import { decideCollectionBranding, decideTagPageBranding } from './branding';
 
 // For the purpose of these tests we don't care about the contents of the logo objects
 const logo = {} as Branding['logo'];
 
-describe('decideCollectionBranding', () => {
-	it('picks branding from a card by their edition', () => {
+void describe('decideCollectionBranding', () => {
+	void it('picks branding from a card by their edition', () => {
 		const cards = [
 			{
 				properties: {
@@ -39,7 +41,7 @@ describe('decideCollectionBranding', () => {
 			editionId: 'UK',
 			isContainerBranding: false,
 		});
-		expect(ukBranding).toMatchObject({
+		assert.deepEqual(ukBranding, {
 			kind: 'paid-content',
 			isFrontBranding: false,
 			branding: {
@@ -58,7 +60,7 @@ describe('decideCollectionBranding', () => {
 			editionId: 'US',
 			isContainerBranding: false,
 		});
-		expect(usBranding).toMatchObject({
+		assert.deepEqual(usBranding, {
 			kind: 'sponsored',
 			isFrontBranding: false,
 			branding: {
@@ -72,7 +74,7 @@ describe('decideCollectionBranding', () => {
 		});
 	});
 
-	it('is paid content derived from multiple cards', () => {
+	void it('is paid content derived from multiple cards', () => {
 		const cardBranding = {
 			brandingType: { name: 'paid-content' as const },
 			sponsorName: 'foo',
@@ -117,14 +119,16 @@ describe('decideCollectionBranding', () => {
 			editionId: 'UK',
 			isContainerBranding: false,
 		});
-		expect(collectionBranding).toMatchObject({
+		assert.deepEqual(collectionBranding, {
 			kind: 'paid-content',
 			isFrontBranding: false,
 			branding: cardBranding,
+			isContainerBranding: false,
+			hasMultipleBranding: false,
 		});
 	});
 
-	it('undefined when not all cards have branding', () => {
+	void it('undefined when not all cards have branding', () => {
 		// The branding we'll apply to each card in this test
 		const collectionBranding = decideCollectionBranding({
 			frontBranding: undefined,
@@ -169,10 +173,10 @@ describe('decideCollectionBranding', () => {
 			editionId: 'UK',
 			isContainerBranding: false,
 		});
-		expect(collectionBranding).toBeUndefined();
+		assert.equal(collectionBranding, undefined);
 	});
 
-	it('is undefined when no cards have branding', () => {
+	void it('is undefined when no cards have branding', () => {
 		const collectionBranding = decideCollectionBranding({
 			frontBranding: undefined,
 			couldDisplayFrontBranding: false,
@@ -196,10 +200,10 @@ describe('decideCollectionBranding', () => {
 			editionId: 'UK',
 			isContainerBranding: false,
 		});
-		expect(collectionBranding).toBeUndefined();
+		assert.equal(collectionBranding, undefined);
 	});
 
-	it('is undefined when cards have different branding types', () => {
+	void it('is undefined when cards have different branding types', () => {
 		const collectionBranding = decideCollectionBranding({
 			frontBranding: undefined,
 			couldDisplayFrontBranding: false,
@@ -253,10 +257,10 @@ describe('decideCollectionBranding', () => {
 			editionId: 'UK',
 			isContainerBranding: false,
 		});
-		expect(collectionBranding).toBeUndefined();
+		assert.equal(collectionBranding, undefined);
 	});
 
-	it('is sponsored branding when all of the branding types are sponsored and the names match', () => {
+	void it('is sponsored branding when all of the branding types are sponsored and the names match', () => {
 		const cardBranding = {
 			brandingType: { name: 'sponsored' as const },
 			sponsorName: 'foo',
@@ -301,7 +305,7 @@ describe('decideCollectionBranding', () => {
 			editionId: 'UK',
 			isContainerBranding: false,
 		});
-		expect(collectionBranding).toStrictEqual({
+		assert.deepEqual(collectionBranding, {
 			kind: 'sponsored',
 			isFrontBranding: false,
 			branding: cardBranding,
@@ -310,7 +314,7 @@ describe('decideCollectionBranding', () => {
 		});
 	});
 
-	it('is undefined when branding cards are sponsored and have different sponsor names', () => {
+	void it('is undefined when branding cards are sponsored and have different sponsor names', () => {
 		// The branding we'll apply to each card in this test
 		const collectionBranding = decideCollectionBranding({
 			frontBranding: undefined,
@@ -365,10 +369,10 @@ describe('decideCollectionBranding', () => {
 			editionId: 'UK',
 			isContainerBranding: false,
 		});
-		expect(collectionBranding).toBeUndefined();
+		assert.equal(collectionBranding, undefined);
 	});
 
-	it('is paid content branding when all of the branding types are paid-content and the names match', () => {
+	void it('is paid content branding when all of the branding types are paid-content and the names match', () => {
 		const collectionBranding = decideCollectionBranding({
 			frontBranding: undefined,
 			couldDisplayFrontBranding: false,
@@ -407,7 +411,7 @@ describe('decideCollectionBranding', () => {
 			editionId: 'UK',
 			isContainerBranding: false,
 		});
-		expect(collectionBranding).toStrictEqual({
+		assert.deepEqual(collectionBranding, {
 			kind: 'paid-content',
 			isFrontBranding: false,
 			branding: {
@@ -421,7 +425,7 @@ describe('decideCollectionBranding', () => {
 		});
 	});
 
-	it('is paid content multiple branding when branding cards are paid-content and have different sponsor names', () => {
+	void it('is paid content multiple branding when branding cards are paid-content and have different sponsor names', () => {
 		const collectionBranding = decideCollectionBranding({
 			frontBranding: undefined,
 			couldDisplayFrontBranding: false,
@@ -460,7 +464,7 @@ describe('decideCollectionBranding', () => {
 			editionId: 'UK',
 			isContainerBranding: false,
 		});
-		expect(collectionBranding).toStrictEqual({
+		assert.deepEqual(collectionBranding, {
 			kind: 'paid-content',
 			isFrontBranding: false,
 			branding: {
@@ -474,7 +478,7 @@ describe('decideCollectionBranding', () => {
 		});
 	});
 
-	it('is front branding when present and possible to display', () => {
+	void it('is front branding when present and possible to display', () => {
 		const collectionBranding = decideCollectionBranding({
 			frontBranding: {
 				brandingType: { name: 'paid-content' },
@@ -487,7 +491,7 @@ describe('decideCollectionBranding', () => {
 			editionId: 'UK',
 			isContainerBranding: false,
 		});
-		expect(collectionBranding).toStrictEqual({
+		assert.deepEqual(collectionBranding, {
 			kind: 'paid-content',
 			isFrontBranding: true,
 			branding: {
@@ -501,7 +505,7 @@ describe('decideCollectionBranding', () => {
 		});
 	});
 
-	it('is undefined when there is front branding (and no card branding) that is not eligible for display on this collection', () => {
+	void it('is undefined when there is front branding (and no card branding) that is not eligible for display on this collection', () => {
 		const collectionBranding = decideCollectionBranding({
 			frontBranding: {
 				brandingType: { name: 'paid-content' },
@@ -514,10 +518,10 @@ describe('decideCollectionBranding', () => {
 			editionId: 'UK',
 			isContainerBranding: false,
 		});
-		expect(collectionBranding).toBeUndefined();
+		assert.equal(collectionBranding, undefined);
 	});
 
-	it('when cards are present', () => {
+	void it('when cards are present', () => {
 		const cardBranding = {
 			brandingType: { name: 'paid-content' as const },
 			sponsorName: 'foo',
@@ -567,7 +571,7 @@ describe('decideCollectionBranding', () => {
 			editionId: 'UK',
 			isContainerBranding: false,
 		});
-		expect(collectionBranding).toStrictEqual({
+		assert.deepEqual(collectionBranding, {
 			kind: 'paid-content',
 			isFrontBranding: false,
 			branding: cardBranding,
@@ -576,7 +580,7 @@ describe('decideCollectionBranding', () => {
 		});
 	});
 
-	it('is undefined when front branding matches card branding, but we are not displaying front branding', () => {
+	void it('is undefined when front branding matches card branding, but we are not displaying front branding', () => {
 		const cardBranding = {
 			brandingType: { name: 'paid-content' as const },
 			sponsorName: 'foo',
@@ -626,12 +630,12 @@ describe('decideCollectionBranding', () => {
 			editionId: 'UK',
 			isContainerBranding: false,
 		});
-		expect(collectionBranding).toBeUndefined();
+		assert.equal(collectionBranding, undefined);
 	});
 });
 
-describe('decideTagPageBranding', () => {
-	it('picks branding from a tag page by their edition', () => {
+void describe('decideTagPageBranding', () => {
+	void it('picks branding from a tag page by their edition', () => {
 		const branding = {
 			brandingType: { name: 'sponsored' },
 			sponsorName: 'Guardian.org',
@@ -643,19 +647,20 @@ describe('decideTagPageBranding', () => {
 			branding,
 		});
 
-		expect(tagPageBranding).toMatchObject({
+		assert.deepEqual(tagPageBranding, {
 			kind: 'sponsored',
 			isFrontBranding: true,
 			branding: {
 				brandingType: { name: 'sponsored' },
 				sponsorName: 'Guardian.org',
 				aboutThisLink: '',
+				logo,
 			},
 			isContainerBranding: false,
 			hasMultipleBranding: false,
 		});
 	});
-	it('is undefined when branding does not have a brandingType name present', () => {
+	void it('is undefined when branding does not have a brandingType name present', () => {
 		const branding = {
 			sponsorName: 'Guardian.org',
 			aboutThisLink: '',
@@ -665,6 +670,6 @@ describe('decideTagPageBranding', () => {
 		const tagPageBranding = decideTagPageBranding({
 			branding,
 		});
-		expect(tagPageBranding).toBeUndefined();
+		assert.equal(tagPageBranding, undefined);
 	});
 });
diff --git a/dotcom-rendering/src/lib/byline.test.ts b/dotcom-rendering/src/lib/byline.node.test.ts
similarity index 77%
rename from dotcom-rendering/src/lib/byline.test.ts
rename to dotcom-rendering/src/lib/byline.node.test.ts
index 0ba313e554d..e6751504d2c 100644
--- a/dotcom-rendering/src/lib/byline.test.ts
+++ b/dotcom-rendering/src/lib/byline.node.test.ts
@@ -1,7 +1,9 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import { getBylineComponentsFromTokens, getSoleContributor } from './byline';
 
-describe('Byline utilities', () => {
-	it('should link a single tag by linking name tokens with Contributor tag titles', () => {
+void describe('Byline utilities', () => {
+	void it('should link a single tag by linking name tokens with Contributor tag titles', () => {
 		const bylineTokens = ['Eva Smith', 'and friends'];
 		const tags = [
 			{
@@ -16,13 +18,13 @@ describe('Byline utilities', () => {
 			tags,
 		);
 
-		expect(bylineComponents).toEqual([
+		assert.deepEqual(bylineComponents, [
 			{ tag: tags[0], token: 'Eva Smith' },
 			'and friends',
 		]);
 	});
 
-	it('should link multiple tags by linking name tokens with Contributor tag titles', () => {
+	void it('should link multiple tags by linking name tokens with Contributor tag titles', () => {
 		const bylineTokens = ['Eva Smith', ' and ', 'Duncan Campbell'];
 		const tags = [
 			{
@@ -41,14 +43,14 @@ describe('Byline utilities', () => {
 			tags,
 		);
 
-		expect(bylineComponents).toEqual([
+		assert.deepEqual(bylineComponents, [
 			{ tag: tags[0], token: 'Eva Smith' },
 			' and ',
 			{ tag: tags[1], token: 'Duncan Campbell' },
 		]);
 	});
 
-	it('should not reuse a contributor tag, to successfully disambiguate identical names', () => {
+	void it('should not reuse a contributor tag, to successfully disambiguate identical names', () => {
 		const bylineTokens = ['Duncan Campbell', ' and ', 'Duncan Campbell'];
 		const tags = [
 			{
@@ -68,16 +70,16 @@ describe('Byline utilities', () => {
 			tags,
 		);
 
-		expect(bylineComponents).toEqual([
+		assert.deepEqual(bylineComponents, [
 			{ tag: tags[0], token: 'Duncan Campbell' },
 			' and ',
 			{ tag: tags[1], token: 'Duncan Campbell' },
 		]);
 	});
 
-	describe('getSoleContributor', () => {
-		describe('returns a contributor', () => {
-			it('Sebastian Köhn, as told to Wilfried Chan', () => {
+	void describe('getSoleContributor', () => {
+		void describe('returns a contributor', () => {
+			void it('Sebastian Köhn, as told to Wilfried Chan', () => {
 				// https://www.theguardian.com/world/2022/jul/23/i-literally-screamed-out-loud-in-pain-my-two-weeks-of-monkeypox-hell
 
 				const soleContributor = getSoleContributor(
@@ -91,10 +93,10 @@ describe('Byline utilities', () => {
 					'Sebastian Köhn, as told to Wilfred Chan',
 				);
 
-				expect(soleContributor?.title).toBe('Wilfred Chan');
+				assert.equal(soleContributor?.title, 'Wilfred Chan');
 			});
 
-			it('Jim Waterson Media editor', () => {
+			void it('Jim Waterson Media editor', () => {
 				// https://www.theguardian.com/media/2021/nov/17/geordie-greig-ousted-as-editor-of-the-daily-mail
 
 				const soleContributor = getSoleContributor(
@@ -116,10 +118,10 @@ describe('Byline utilities', () => {
 					'Jim Waterson Media editor',
 				);
 
-				expect(soleContributor?.title).toBe('Jim Waterson');
+				assert.equal(soleContributor?.title, 'Jim Waterson');
 			});
 
-			it('First Dog on the Moon', () => {
+			void it('First Dog on the Moon', () => {
 				// https://www.theguardian.com/commentisfree/2022/jul/22/europe-is-ablaze-italian-glaciers-are-collapsing-the-climate-crisis-is-here
 
 				const soleContributor = getSoleContributor(
@@ -133,10 +135,10 @@ describe('Byline utilities', () => {
 					'First Dog on the Moon',
 				);
 
-				expect(soleContributor?.title).toBe('First Dog on the Moon');
+				assert.equal(soleContributor?.title, 'First Dog on the Moon');
 			});
 
-			it('Sam Levine in New York', () => {
+			void it('Sam Levine in New York', () => {
 				// https://www.theguardian.com/us-news/2022/jul/22/january-6-panel-american-democracy-nose-dive
 
 				const soleContributor = getSoleContributor(
@@ -150,12 +152,12 @@ describe('Byline utilities', () => {
 					'Sam Levine in New York',
 				);
 
-				expect(soleContributor?.title).toBe('Sam Levine');
+				assert.equal(soleContributor?.title, 'Sam Levine');
 			});
 		});
 
-		describe('returns `undefined`', () => {
-			it('Sam Levin in Los Angeles and Sam Levine in New York', () => {
+		void describe('returns `undefined`', () => {
+			void it('Sam Levin in Los Angeles and Sam Levine in New York', () => {
 				// https://www.theguardian.com/us-news/2020/oct/12/republicans-election-2020-unauthorized-ballot-boxes
 
 				const soleContributor = getSoleContributor(
@@ -174,10 +176,10 @@ describe('Byline utilities', () => {
 					],
 					'Sam Levin in Los Angeles and Sam Levine in New York',
 				);
-				expect(soleContributor).toBe(undefined);
+				assert.equal(soleContributor, undefined);
 			});
 
-			it('Gabriel Smith', () => {
+			void it('Gabriel Smith', () => {
 				const soleContributor = getSoleContributor(
 					[
 						{
@@ -189,10 +191,10 @@ describe('Byline utilities', () => {
 					],
 					'Gabriel Smith',
 				);
-				expect(soleContributor).toBe(undefined);
+				assert.equal(soleContributor, undefined);
 			});
 
-			it('Zoe Williams and others', () => {
+			void it('Zoe Williams and others', () => {
 				// https://www.theguardian.com/commentisfree/2022/jul/20/britain-next-prime-minister-rishi-sunak-liz-truss-conservative-leader
 
 				const soleContributor = getSoleContributor(
@@ -227,10 +229,10 @@ describe('Byline utilities', () => {
 					'Zoe Williams and others',
 				);
 
-				expect(soleContributor).toBe(undefined);
+				assert.equal(soleContributor, undefined);
 			});
 
-			it('Paul MacInnes, Nesrine Malik, Julie Bindel, Peter Preston', () => {
+			void it('Paul MacInnes, Nesrine Malik, Julie Bindel, Peter Preston', () => {
 				// https://www.theguardian.com/commentisfree/2011/dec/30/person-of-2011-writers-verdict
 
 				const soleContributor = getSoleContributor(
@@ -261,7 +263,7 @@ describe('Byline utilities', () => {
 					'Paul MacInnes, Nesrine Malik, Julie Bindel, Peter Preston',
 				);
 
-				expect(soleContributor).toBe(undefined);
+				assert.equal(soleContributor, undefined);
 			});
 		});
 	});
diff --git a/dotcom-rendering/src/lib/canRenderAds.test.ts b/dotcom-rendering/src/lib/canRenderAds.node.test.ts
similarity index 50%
rename from dotcom-rendering/src/lib/canRenderAds.test.ts
rename to dotcom-rendering/src/lib/canRenderAds.node.test.ts
index ddf11a270fa..72a0e61b5ea 100644
--- a/dotcom-rendering/src/lib/canRenderAds.test.ts
+++ b/dotcom-rendering/src/lib/canRenderAds.node.test.ts
@@ -1,25 +1,27 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import { Standard } from '../../fixtures/generated/fe-articles/Standard';
 import { enhanceArticleType } from '../types/article';
 import { canRenderAds } from './canRenderAds';
 
 const standardPage = enhanceArticleType(Standard, 'Web');
 
-describe('canRenderAds', () => {
-	it('shows ads by default', () => {
-		expect(canRenderAds(standardPage.frontendData)).toBe(true);
+void describe('canRenderAds', () => {
+	void it('shows ads by default', () => {
+		assert.equal(canRenderAds(standardPage.frontendData), true);
 	});
 
-	it('does not show ads if user is ad-free', () => {
+	void it('does not show ads if user is ad-free', () => {
 		const adFreePage = Object.assign({}, standardPage.frontendData);
 		adFreePage.isAdFreeUser = true;
 
-		expect(canRenderAds(adFreePage)).toBe(false);
+		assert.equal(canRenderAds(adFreePage), false);
 	});
 
-	it('does not show ads if page should not display them', () => {
+	void it('does not show ads if page should not display them', () => {
 		const adFreePage = Object.assign({}, standardPage.frontendData);
 		adFreePage.shouldHideAds = true;
 
-		expect(canRenderAds(adFreePage)).toBe(false);
+		assert.equal(canRenderAds(adFreePage), false);
 	});
 });
diff --git a/dotcom-rendering/src/lib/cardHelpers.test.ts b/dotcom-rendering/src/lib/cardHelpers.node.test.ts
similarity index 64%
rename from dotcom-rendering/src/lib/cardHelpers.test.ts
rename to dotcom-rendering/src/lib/cardHelpers.node.test.ts
index a0376496b99..ec6dbef7e3f 100644
--- a/dotcom-rendering/src/lib/cardHelpers.test.ts
+++ b/dotcom-rendering/src/lib/cardHelpers.node.test.ts
@@ -1,7 +1,9 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import type { DCRContainerPalette } from '../types/front';
 import { cardHasDarkBackground } from './cardHelpers';
 
-describe('cardHasDarkBackground', () => {
+void describe('cardHasDarkBackground', () => {
 	const testCases = [
 		{
 			containerPalette: undefined,
@@ -32,12 +34,12 @@ describe('cardHasDarkBackground', () => {
 		expectedResult: boolean;
 	}[];
 
-	it.each(testCases)(
-		'returns $expectedResult for $format format, $containerPalette containerPalette',
-		({ containerPalette, expectedResult }) => {
-			expect(cardHasDarkBackground(containerPalette)).toBe(
+	for (const { containerPalette, expectedResult } of testCases) {
+		void it(`returns ${expectedResult} for $format format, ${containerPalette} containerPalette`, () => {
+			assert.equal(
+				cardHasDarkBackground(containerPalette),
 				expectedResult,
 			);
-		},
-	);
+		});
+	}
 });
diff --git a/dotcom-rendering/src/lib/decide-cation.test.ts b/dotcom-rendering/src/lib/decide-cation.node.test.ts
similarity index 55%
rename from dotcom-rendering/src/lib/decide-cation.test.ts
rename to dotcom-rendering/src/lib/decide-cation.node.test.ts
index ef4fc81d1be..43da6caf249 100644
--- a/dotcom-rendering/src/lib/decide-cation.test.ts
+++ b/dotcom-rendering/src/lib/decide-cation.node.test.ts
@@ -1,3 +1,5 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import type {
 	EmbedBlockElement,
 	ImageBlockElement,
@@ -5,23 +7,24 @@ import type {
 } from '../types/content';
 import { decideMainMediaCaption } from './decide-caption';
 
-describe('decideMainMediaCaption', () => {
-	describe('when mainMedia is not supported', () => {
-		it('undefined returns an empty string', () => {
-			expect(decideMainMediaCaption(undefined)).toEqual('');
+void describe('decideMainMediaCaption', () => {
+	void describe('when mainMedia is not supported', () => {
+		void it('undefined returns an empty string', () => {
+			assert.deepEqual(decideMainMediaCaption(undefined), '');
 		});
-		it('a text block returns an empty string', () => {
-			expect(
+		void it('a text block returns an empty string', () => {
+			assert.deepEqual(
 				decideMainMediaCaption({
 					elementId: 'test-id',
 					html: '<p>test</p>',
 					_type: 'model.dotcomrendering.pageElements.TextBlockElement',
 				} as TextBlockElement),
-			).toEqual('');
+				'',
+			);
 		});
 	});
 
-	describe('ImageBlockElement', () => {
+	void describe('ImageBlockElement', () => {
 		const mockImageBlockElement = {
 			elementId: 'mock-element-id',
 			data: {},
@@ -29,23 +32,24 @@ describe('decideMainMediaCaption', () => {
 			_type: 'model.dotcomrendering.pageElements.ImageBlockElement',
 		} as ImageBlockElement;
 
-		it('returns an empty string if there is no caption, displayCredit, or credit', () => {
-			expect(decideMainMediaCaption(mockImageBlockElement)).toEqual('');
+		void it('returns an empty string if there is no caption, displayCredit, or credit', () => {
+			assert.deepEqual(decideMainMediaCaption(mockImageBlockElement), '');
 		});
 
-		it('includes the caption, if it exists', () => {
-			expect(
+		void it('includes the caption, if it exists', () => {
+			assert.deepEqual(
 				decideMainMediaCaption({
 					...mockImageBlockElement,
 					data: {
 						caption: 'image block caption',
 					},
 				}),
-			).toEqual('image block caption');
+				'image block caption',
+			);
 		});
 
-		it('includes the credit, if it should be displayed', () => {
-			expect(
+		void it('includes the credit, if it should be displayed', () => {
+			assert.deepEqual(
 				decideMainMediaCaption({
 					...mockImageBlockElement,
 					displayCredit: true,
@@ -53,11 +57,12 @@ describe('decideMainMediaCaption', () => {
 						credit: 'image block display credit',
 					},
 				}),
-			).toEqual('image block display credit');
+				'image block display credit',
+			);
 		});
 
-		it('does not include the credit, if it should not be displayed', () => {
-			expect(
+		void it('does not include the credit, if it should not be displayed', () => {
+			assert.deepEqual(
 				decideMainMediaCaption({
 					...mockImageBlockElement,
 					displayCredit: false,
@@ -65,11 +70,12 @@ describe('decideMainMediaCaption', () => {
 						credit: 'image block display credit',
 					},
 				}),
-			).toEqual('');
+				'',
+			);
 		});
 
-		it('includes both the credit and caption, if they exist', () => {
-			expect(
+		void it('includes both the credit and caption, if they exist', () => {
+			assert.deepEqual(
 				decideMainMediaCaption({
 					...mockImageBlockElement,
 					displayCredit: true,
@@ -78,24 +84,26 @@ describe('decideMainMediaCaption', () => {
 						credit: 'mock display credit',
 					},
 				}),
-			).toEqual('mock caption mock display credit');
+				'mock caption mock display credit',
+			);
 		});
 	});
 
-	describe('EmbedBlockElement', () => {
-		it('returns an empty string if there is no caption', () => {
-			expect(
+	void describe('EmbedBlockElement', () => {
+		void it('returns an empty string if there is no caption', () => {
+			assert.deepEqual(
 				decideMainMediaCaption({
 					elementId: 'test-id',
 					html: '<p>test</p>',
 					isMandatory: false,
 					_type: 'model.dotcomrendering.pageElements.EmbedBlockElement',
 				} as EmbedBlockElement),
-			).toEqual('');
+				'',
+			);
 		});
 
-		it('returns the correct caption, if exists', () => {
-			expect(
+		void it('returns the correct caption, if exists', () => {
+			assert.deepEqual(
 				decideMainMediaCaption({
 					elementId: 'test-id',
 					html: '<p>test</p>',
@@ -103,7 +111,8 @@ describe('decideMainMediaCaption', () => {
 					caption: 'test caption',
 					_type: 'model.dotcomrendering.pageElements.EmbedBlockElement',
 				} as EmbedBlockElement),
-			).toEqual('test caption');
+				'test caption',
+			);
 		});
 	});
 });
diff --git a/dotcom-rendering/src/lib/edition.node.test.ts b/dotcom-rendering/src/lib/edition.node.test.ts
new file mode 100644
index 00000000000..56db4a2a398
--- /dev/null
+++ b/dotcom-rendering/src/lib/edition.node.test.ts
@@ -0,0 +1,56 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+import {
+	editionalisedPages,
+	editionList,
+	isEditionalisedPage,
+	isNetworkFront,
+} from './edition';
+
+const everyNetworkFront = editionList.map((edition) => edition.pageId);
+
+const everyEditionalisedPage = editionList
+	.map((edition) =>
+		editionalisedPages.map((page) => `${edition.pageId}/${page}`),
+	)
+	.flat();
+
+void describe('is network front', () => {
+	void it('returns true if pageId is a network front', () => {
+		assert.equal(
+			everyNetworkFront.every((page) => isNetworkFront(page)),
+			true,
+		);
+	});
+	void it('returns false if pageId is NOT a network front', () => {
+		assert.equal(everyEditionalisedPage.every(isNetworkFront), false);
+		assert.equal(isNetworkFront('eu'), false);
+		assert.equal(isNetworkFront('int'), false);
+		assert.equal(isNetworkFront('uk/'), false);
+	});
+});
+
+void describe('is editionalised page', () => {
+	void it('returns true if pageId is editionalised', () => {
+		assert.equal(
+			everyEditionalisedPage.every((page) => isEditionalisedPage(page)),
+			true,
+		);
+	});
+	void it('returns false if pageId is NOT editionalised', () => {
+		assert.equal(
+			everyNetworkFront.every((page) => isEditionalisedPage(page)),
+			false,
+		);
+		assert.equal(isEditionalisedPage('uk'), false);
+		assert.equal(isEditionalisedPage('au'), false);
+		assert.equal(isEditionalisedPage('international'), false);
+		assert.equal(isEditionalisedPage('travel'), false);
+		assert.equal(isEditionalisedPage('culture'), false);
+		assert.equal(isEditionalisedPage('lifeandstyle'), false);
+		assert.equal(
+			isEditionalisedPage('lifeandstyle/health-and-wellbeing'),
+			false,
+		);
+	});
+});
diff --git a/dotcom-rendering/src/lib/edition.test.ts b/dotcom-rendering/src/lib/edition.test.ts
deleted file mode 100644
index 406e2a311a9..00000000000
--- a/dotcom-rendering/src/lib/edition.test.ts
+++ /dev/null
@@ -1,50 +0,0 @@
-import {
-	editionalisedPages,
-	editionList,
-	isEditionalisedPage,
-	isNetworkFront,
-} from './edition';
-
-const everyNetworkFront = editionList.map((edition) => edition.pageId);
-
-const everyEditionalisedPage = editionList
-	.map((edition) =>
-		editionalisedPages.map((page) => `${edition.pageId}/${page}`),
-	)
-	.flat();
-
-describe('is network front', () => {
-	it('returns true if pageId is a network front', () => {
-		expect(everyNetworkFront.every((page) => isNetworkFront(page))).toBe(
-			true,
-		);
-	});
-	it('returns false if pageId is NOT a network front', () => {
-		expect(everyEditionalisedPage.every(isNetworkFront)).toBe(false);
-		expect(isNetworkFront('eu')).toBe(false);
-		expect(isNetworkFront('int')).toBe(false);
-		expect(isNetworkFront('uk/')).toBe(false);
-	});
-});
-
-describe('is editionalised page', () => {
-	it('returns true if pageId is editionalised', () => {
-		expect(
-			everyEditionalisedPage.every((page) => isEditionalisedPage(page)),
-		).toBe(true);
-	});
-	it('returns false if pageId is NOT editionalised', () => {
-		expect(
-			everyNetworkFront.every((page) => isEditionalisedPage(page)),
-		).toBe(false);
-		expect(isEditionalisedPage('uk')).toBe(false);
-		expect(isEditionalisedPage('au')).toBe(false);
-		expect(isEditionalisedPage('international')).toBe(false);
-		expect(isEditionalisedPage('travel')).toBe(false);
-		expect(isEditionalisedPage('culture')).toBe(false);
-		expect(isEditionalisedPage('lifeandstyle')).toBe(false);
-		expect(isEditionalisedPage('lifeandstyle/health-and-wellbeing')).toBe(
-			false,
-		);
-	});
-});
diff --git a/dotcom-rendering/src/lib/formatAttrString.node.test.ts b/dotcom-rendering/src/lib/formatAttrString.node.test.ts
new file mode 100644
index 00000000000..2ec3aba6e4b
--- /dev/null
+++ b/dotcom-rendering/src/lib/formatAttrString.node.test.ts
@@ -0,0 +1,32 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+import { formatAttrString } from './formatAttrString';
+
+const expectedOutput = 'this-headline-should-be-converted';
+
+void describe('formatAttrString', () => {
+	void it('Lowercases all', () => {
+		const input = 'This Headline Should Be Converted';
+		assert.equal(formatAttrString(input), expectedOutput);
+	});
+
+	void it('Converts spaces to hyphens', () => {
+		const input = 'this headline should be converted';
+		assert.equal(formatAttrString(input), expectedOutput);
+	});
+
+	void it('Removes anything but spaces and letters', () => {
+		const input = '/this headline should be converted.';
+		assert.equal(formatAttrString(input), expectedOutput);
+	});
+
+	void it('Does not remove numbers', () => {
+		const input = 'this headline should be converted 12';
+		assert.equal(formatAttrString(input), `${expectedOutput}-12`);
+	});
+
+	void it('Puts it all together', () => {
+		const input = '/this Headline should be converted. 12';
+		assert.equal(formatAttrString(input), `${expectedOutput}-12`);
+	});
+});
diff --git a/dotcom-rendering/src/lib/formatAttrString.test.ts b/dotcom-rendering/src/lib/formatAttrString.test.ts
deleted file mode 100644
index 726778855f4..00000000000
--- a/dotcom-rendering/src/lib/formatAttrString.test.ts
+++ /dev/null
@@ -1,30 +0,0 @@
-import { formatAttrString } from './formatAttrString';
-
-const expectedOutput = 'this-headline-should-be-converted';
-
-describe('formatAttrString', () => {
-	it('Lowercases all', () => {
-		const input = 'This Headline Should Be Converted';
-		expect(formatAttrString(input)).toBe(expectedOutput);
-	});
-
-	it('Converts spaces to hyphens', () => {
-		const input = 'this headline should be converted';
-		expect(formatAttrString(input)).toBe(expectedOutput);
-	});
-
-	it('Removes anything but spaces and letters', () => {
-		const input = '/this headline should be converted.';
-		expect(formatAttrString(input)).toBe(expectedOutput);
-	});
-
-	it('Does not remove numbers', () => {
-		const input = 'this headline should be converted 12';
-		expect(formatAttrString(input)).toBe(`${expectedOutput}-12`);
-	});
-
-	it('Puts it all together', () => {
-		const input = '/this Headline should be converted. 12';
-		expect(formatAttrString(input)).toBe(`${expectedOutput}-12`);
-	});
-});
diff --git a/dotcom-rendering/src/lib/formatCount.node.test.ts b/dotcom-rendering/src/lib/formatCount.node.test.ts
new file mode 100644
index 00000000000..b13c5ea64bb
--- /dev/null
+++ b/dotcom-rendering/src/lib/formatCount.node.test.ts
@@ -0,0 +1,21 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+import { formatCount } from './formatCount';
+
+void describe('formatCount', () => {
+	void it('formats simple numbers', () => {
+		assert.deepEqual(formatCount(123), { short: '123', long: '123' });
+	});
+	void it('formats medium numbers', () => {
+		assert.deepEqual(formatCount(9876), { short: '9876', long: '9,876' });
+	});
+	void it('formats very long numbers', () => {
+		assert.deepEqual(formatCount(92878), { short: '93k', long: '92,878' });
+	});
+	void it('returns zero for zero', () => {
+		assert.deepEqual(formatCount(0), { short: '0', long: '0' });
+	});
+	void it('returns an ellipsis for undefined', () => {
+		assert.deepEqual(formatCount(), { short: '…', long: '…' });
+	});
+});
diff --git a/dotcom-rendering/src/lib/formatCount.test.ts b/dotcom-rendering/src/lib/formatCount.test.ts
deleted file mode 100644
index f16401b2823..00000000000
--- a/dotcom-rendering/src/lib/formatCount.test.ts
+++ /dev/null
@@ -1,19 +0,0 @@
-import { formatCount } from './formatCount';
-
-describe('formatCount', () => {
-	it('formats simple numbers', () => {
-		expect(formatCount(123)).toEqual({ short: '123', long: '123' });
-	});
-	it('formats medium numbers', () => {
-		expect(formatCount(9876)).toEqual({ short: '9876', long: '9,876' });
-	});
-	it('formats very long numbers', () => {
-		expect(formatCount(92878)).toEqual({ short: '93k', long: '92,878' });
-	});
-	it('returns zero for zero', () => {
-		expect(formatCount(0)).toEqual({ short: '0', long: '0' });
-	});
-	it('returns an ellipsis for undefined', () => {
-		expect(formatCount()).toEqual({ short: '…', long: '…' });
-	});
-});
diff --git a/dotcom-rendering/src/lib/getFrontsAdPositions.test.ts b/dotcom-rendering/src/lib/getFrontsAdPositions.node.test.ts
similarity index 80%
rename from dotcom-rendering/src/lib/getFrontsAdPositions.test.ts
rename to dotcom-rendering/src/lib/getFrontsAdPositions.node.test.ts
index bec47bd6ab9..efa9950309f 100644
--- a/dotcom-rendering/src/lib/getFrontsAdPositions.test.ts
+++ b/dotcom-rendering/src/lib/getFrontsAdPositions.node.test.ts
@@ -1,3 +1,5 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import {
 	brandedTestCollections,
 	largeFlexibleGeneralCollection,
@@ -32,8 +34,8 @@ const defaultTestCollections: AdCandidate[] = [...Array<number>(12)].map(
 	() => ({ ...testCollection }),
 );
 
-describe('Mobile Ads', () => {
-	it(`Should not insert ad after container if it's the first one and it's a thrasher`, () => {
+void describe('Mobile Ads', () => {
+	void it(`Should not insert ad after container if it's the first one and it's a thrasher`, () => {
 		const testCollections = [
 			{ ...testCollection, collectionType: 'fixed/thrasher' },
 			...defaultTestCollections,
@@ -41,19 +43,19 @@ describe('Mobile Ads', () => {
 
 		const mobileAdPositions = getMobileAdPositions(testCollections, 'uk');
 
-		expect(mobileAdPositions).not.toContain(0);
+		assert(!mobileAdPositions.includes(0));
 	});
 
-	it(`should not insert an ad in the merchandising-high position`, () => {
+	void it(`should not insert an ad in the merchandising-high position`, () => {
 		const testCollections = [
 			...defaultTestCollections.slice(0, 3),
 			{ ...testCollection, collectionType: 'news/most-popular' },
 		] satisfies AdCandidate[];
 		const mobileAdPositions = getMobileAdPositions(testCollections, 'uk');
-		expect(mobileAdPositions).not.toContain(3);
+		assert(!mobileAdPositions.includes(3));
 	});
 
-	it('Should not insert ad before a thrasher container', () => {
+	void it('Should not insert ad before a thrasher container', () => {
 		const testCollections = [...defaultTestCollections];
 		testCollections.splice(5, 0, {
 			...testCollection,
@@ -66,11 +68,11 @@ describe('Mobile Ads', () => {
 
 		const mobileAdPositions = getMobileAdPositions(testCollections, 'uk');
 
-		expect(mobileAdPositions).not.toContain(6);
-		expect(mobileAdPositions).not.toContain(8);
+		assert(!mobileAdPositions.includes(6));
+		assert(!mobileAdPositions.includes(8));
 	});
 
-	it(`Should allow inserting an ad before a thrasher container if it's a filter page`, () => {
+	void it(`Should allow inserting an ad before a thrasher container if it's a filter page`, () => {
 		const testCollections = [...defaultTestCollections];
 		testCollections.splice(5, 0, {
 			...testCollection,
@@ -86,12 +88,12 @@ describe('Mobile Ads', () => {
 			'uk/thefilter',
 		);
 
-		expect(mobileAdPositions).toContain(6);
-		expect(mobileAdPositions).toContain(8);
+		assert(mobileAdPositions.includes(6));
+		assert(mobileAdPositions.includes(8));
 	});
 
 	// We used https://www.theguardian.com/uk/commentisfree as a blueprint
-	it('Non-network front, with more than 4 collections, without thrashers', () => {
+	void it('Non-network front, with more than 4 collections, without thrashers', () => {
 		const testCollections: AdCandidate[] = [
 			{ ...testCollection, collectionType: 'flexible/general' }, // Ad position (0)
 			{ ...testCollection, collectionType: 'flexible/general' },
@@ -110,11 +112,11 @@ describe('Mobile Ads', () => {
 
 		const mobileAdPositions = getMobileAdPositions(testCollections, 'uk');
 
-		expect(mobileAdPositions).toEqual([0, 2, 4, 6, 8]);
+		assert.deepEqual(mobileAdPositions, [0, 2, 4, 6, 8]);
 	});
 
 	// We used https://www.theguardian.com/uk as a blueprint
-	it('UK Network Front, with more than 4 collections, with thrashers at various places', () => {
+	void it('UK Network Front, with more than 4 collections, with thrashers at various places', () => {
 		const testCollections: AdCandidate[] = [
 			{ ...testCollection, collectionType: 'flexible/general' }, // Ad position (0)
 			{ ...testCollection, collectionType: 'static/medium/4' },
@@ -144,11 +146,11 @@ describe('Mobile Ads', () => {
 
 		const mobileAdPositions = getMobileAdPositions(testCollections, 'uk');
 
-		expect(mobileAdPositions).toEqual([0, 2, 4, 8, 11, 14, 17, 19]);
+		assert.deepEqual(mobileAdPositions, [0, 2, 4, 8, 11, 14, 17, 19]);
 	});
 
 	// We used https://www.theguardian.com/international as a blueprint
-	it('International Network Front, with more than 4 collections, with thrashers at various places', () => {
+	void it('International Network Front, with more than 4 collections, with thrashers at various places', () => {
 		const testCollections: AdCandidate[] = [
 			{ ...testCollection, collectionType: 'flexible/general' }, // Ad position (0)
 			{ ...testCollection, collectionType: 'static/medium/4' },
@@ -174,11 +176,11 @@ describe('Mobile Ads', () => {
 
 		const mobileAdPositions = getMobileAdPositions(testCollections, 'uk');
 
-		expect(mobileAdPositions).toEqual([0, 2, 5, 7, 11, 14, 16]);
+		assert.deepEqual(mobileAdPositions, [0, 2, 5, 7, 11, 14, 16]);
 	});
 
 	// We used https://www.theguardian.com/us as a blueprint
-	it('US Network Front, with more than 4 collections, with thrashers at various places', () => {
+	void it('US Network Front, with more than 4 collections, with thrashers at various places', () => {
 		const testCollections: AdCandidate[] = [
 			{ ...testCollection, collectionType: 'flexible/general' }, // Ad position (0)
 			{ ...testCollection, collectionType: 'static/medium/4' },
@@ -205,11 +207,11 @@ describe('Mobile Ads', () => {
 
 		const mobileAdPositions = getMobileAdPositions(testCollections, 'uk');
 
-		expect(mobileAdPositions).toEqual([0, 2, 5, 9, 12, 14, 16]);
+		assert.deepEqual(mobileAdPositions, [0, 2, 5, 9, 12, 14, 16]);
 	});
 
 	// We used https://www.theguardian.com/uk/lifeandstyle as a blueprint
-	it('Lifeandstyle front, with more than 4 collections, with thrashers at various places', () => {
+	void it('Lifeandstyle front, with more than 4 collections, with thrashers at various places', () => {
 		const testCollections: AdCandidate[] = [
 			{ ...testCollection, collectionType: 'flexible/special' }, // Ad position (0)
 			{ ...testCollection, collectionType: 'flexible/general' }, // Ignored - before thrasher
@@ -231,11 +233,11 @@ describe('Mobile Ads', () => {
 
 		const mobileAdPositions = getMobileAdPositions(testCollections, 'uk');
 
-		expect(mobileAdPositions).toEqual([0, 3, 6, 9, 12]);
+		assert.deepEqual(mobileAdPositions, [0, 3, 6, 9, 12]);
 	});
 
 	// We used https://www.theguardian.com/tone/recipes as a blueprint
-	it('Recipes front, with more than 4 collections, with thrasher at the first position', () => {
+	void it('Recipes front, with more than 4 collections, with thrasher at the first position', () => {
 		const testCollections: AdCandidate[] = [
 			{ ...testCollection, collectionType: 'fixed/thrasher' }, // Ignored - is first container and thrasher
 			{ ...testCollection, collectionType: 'flexible/general' }, // Ad position (1)
@@ -255,10 +257,10 @@ describe('Mobile Ads', () => {
 
 		const mobileAdPositions = getMobileAdPositions(testCollections, 'uk');
 
-		expect(mobileAdPositions).toEqual([1, 3, 5, 7, 9]);
+		assert.deepEqual(mobileAdPositions, [1, 3, 5, 7, 9]);
 	});
 
-	it('Europe Network Front, with more than 4 collections and thrashers in various places', () => {
+	void it('Europe Network Front, with more than 4 collections and thrashers in various places', () => {
 		const testCollections: AdCandidate[] = [
 			{
 				...testCollection,
@@ -362,39 +364,39 @@ describe('Mobile Ads', () => {
 
 		const mobileAdPositions = getMobileAdPositions(testCollections, 'uk');
 
-		expect(mobileAdPositions).toEqual([4, 6, 8, 13, 18]);
+		assert.deepEqual(mobileAdPositions, [4, 6, 8, 13, 18]);
 	});
 });
 
-describe('Desktop Ads', () => {
-	it('calculates ad positions correctly for an example of the UK network front', () => {
+void describe('Desktop Ads', () => {
+	void it('calculates ad positions correctly for an example of the UK network front', () => {
 		const adPositions = getDesktopAdPositions(testCollectionsUk, 'uk');
 
-		expect(adPositions).toEqual([3, 6, 8, 14, 17]);
+		assert.deepEqual(adPositions, [3, 6, 8, 14, 17]);
 	});
 
-	it('calculates ad positions correctly for an example of the US network front', () => {
+	void it('calculates ad positions correctly for an example of the US network front', () => {
 		const adPositions = getDesktopAdPositions(testCollectionsUs, 'us');
 
-		expect(adPositions).toEqual([3, 6, 10, 12, 19]);
+		assert.deepEqual(adPositions, [3, 6, 10, 12, 19]);
 	});
 
-	it('does NOT insert ads above or below branded content', () => {
+	void it('does NOT insert ads above or below branded content', () => {
 		const adPositions = getDesktopAdPositions(brandedTestCollections, 'uk');
 
-		expect(adPositions).toEqual([]);
+		assert.deepEqual(adPositions, []);
 	});
 
-	it('does NOT insert ads above secondary level containers', () => {
+	void it('does NOT insert ads above secondary level containers', () => {
 		const adPositions = getDesktopAdPositions(
 			testCollectionsWithSecondaryLevel,
 			'europe',
 		);
 
-		expect(adPositions).toEqual([]);
+		assert.deepEqual(adPositions, []);
 	});
 
-	it('inserts a maximum of 8 ads for fronts', () => {
+	void it('inserts a maximum of 8 ads for fronts', () => {
 		const adPositions = getDesktopAdPositions(
 			// 10x number of test collections in fixture to reach maximum level
 			new Array<DCRCollectionType[]>(10)
@@ -403,13 +405,13 @@ describe('Desktop Ads', () => {
 			'europe',
 		);
 
-		expect(adPositions.length).toEqual(8);
+		assert.deepEqual(adPositions.length, 8);
 	});
 });
 
-describe('inserting an ad after the first collection', () => {
-	describe('on mobile', () => {
-		it('inserts an ad after the first collection if it is a LARGE flexible general container', () => {
+void describe('inserting an ad after the first collection', () => {
+	void describe('on mobile', () => {
+		void it('inserts an ad after the first collection if it is a LARGE flexible general container', () => {
 			const adPositions = getMobileAdPositions(
 				[
 					...largeFlexibleGeneralCollection,
@@ -427,11 +429,11 @@ describe('inserting an ad after the first collection', () => {
 				'uk',
 			);
 
-			expect(adPositions).toContain(0);
-			expect(adPositions).not.toContain(1);
+			assert(adPositions.includes(0));
+			assert(!adPositions.includes(1));
 		});
 
-		it('inserts an ad after the first collection if it is a LARGE flexible special container', () => {
+		void it('inserts an ad after the first collection if it is a LARGE flexible special container', () => {
 			const adPositions = getMobileAdPositions(
 				[
 					...largeFlexibleSpecialCollection,
@@ -449,11 +451,11 @@ describe('inserting an ad after the first collection', () => {
 				'uk',
 			);
 
-			expect(adPositions).toContain(0);
-			expect(adPositions).not.toContain(1);
+			assert(adPositions.includes(0));
+			assert(!adPositions.includes(1));
 		});
 
-		it('does NOT insert an ad after the first collection if it is a SMALL flexible general container', () => {
+		void it('does NOT insert an ad after the first collection if it is a SMALL flexible general container', () => {
 			const adPositions = getMobileAdPositions(
 				[
 					...smallFlexibleGeneralCollection,
@@ -466,10 +468,10 @@ describe('inserting an ad after the first collection', () => {
 				'uk',
 			);
 
-			expect(adPositions).not.toContain(0);
+			assert(!adPositions.includes(0));
 		});
 
-		it('does NOT insert an ad after the first collection if it is a SMALL flexible special container', () => {
+		void it('does NOT insert an ad after the first collection if it is a SMALL flexible special container', () => {
 			const adPositions = getMobileAdPositions(
 				[
 					...smallFlexibleSpecialCollection,
@@ -482,12 +484,12 @@ describe('inserting an ad after the first collection', () => {
 				'uk',
 			);
 
-			expect(adPositions).not.toContain(0);
+			assert(!adPositions.includes(0));
 		});
 	});
 
-	describe('on desktop', () => {
-		it('inserts an ad before the second collection if it is preceded by a LARGE flexible general container', () => {
+	void describe('on desktop', () => {
+		void it('inserts an ad before the second collection if it is preceded by a LARGE flexible general container', () => {
 			const adPositions = getDesktopAdPositions(
 				[
 					...largeFlexibleGeneralCollection,
@@ -505,11 +507,11 @@ describe('inserting an ad after the first collection', () => {
 				'uk',
 			);
 
-			expect(adPositions).toContain(1);
-			expect(adPositions).not.toContain(2);
+			assert(adPositions.includes(1));
+			assert(!adPositions.includes(2));
 		});
 
-		it('inserts an ad before the second collection if it is preceded by a LARGE flexible special container', () => {
+		void it('inserts an ad before the second collection if it is preceded by a LARGE flexible special container', () => {
 			const adPositions = getDesktopAdPositions(
 				[
 					...largeFlexibleSpecialCollection,
@@ -527,11 +529,11 @@ describe('inserting an ad after the first collection', () => {
 				'uk',
 			);
 
-			expect(adPositions).toContain(1);
-			expect(adPositions).not.toContain(2);
+			assert(adPositions.includes(1));
+			assert(!adPositions.includes(2));
 		});
 
-		it('does NOT insert an ad before the second collection if it is preceded by a SMALL flexible general container', () => {
+		void it('does NOT insert an ad before the second collection if it is preceded by a SMALL flexible general container', () => {
 			const adPositions = getDesktopAdPositions(
 				[
 					...smallFlexibleGeneralCollection,
@@ -549,10 +551,10 @@ describe('inserting an ad after the first collection', () => {
 				'uk',
 			);
 
-			expect(adPositions).not.toContain(1);
+			assert(!adPositions.includes(1));
 		});
 
-		it('does NOT insert an ad before the second collection if it is preceded by a SMALL flexible special container', () => {
+		void it('does NOT insert an ad before the second collection if it is preceded by a SMALL flexible special container', () => {
 			const adPositions = getDesktopAdPositions(
 				[
 					...smallFlexibleSpecialCollection,
@@ -570,27 +572,27 @@ describe('inserting an ad after the first collection', () => {
 				'uk',
 			);
 
-			expect(adPositions).not.toContain(1);
+			assert(!adPositions.includes(1));
 		});
 	});
 });
 
-describe('removeConsecutiveAdSlotsReducer', () => {
-	it('removes consecutive slots from array of all consecutive numbers', () => {
+void describe('removeConsecutiveAdSlotsReducer', () => {
+	void it('removes consecutive slots from array of all consecutive numbers', () => {
 		const arr = [0, 1, 2, 3, 4, 5];
 		const result = arr.reduce(removeConsecutiveAdSlotsReducer, []);
-		expect(result).toEqual([0, 2, 4]);
+		assert.deepEqual(result, [0, 2, 4]);
 	});
 
-	it('removes consecutive slots from array of some consecutive numbers', () => {
+	void it('removes consecutive slots from array of some consecutive numbers', () => {
 		const arr = [0, 3, 7, 11, 12, 13, 19, 20];
 		const result = arr.reduce(removeConsecutiveAdSlotsReducer, []);
-		expect(result).toEqual([0, 3, 7, 11, 13, 19]);
+		assert.deepEqual(result, [0, 3, 7, 11, 13, 19]);
 	});
 
-	it('handles empty array', () => {
+	void it('handles empty array', () => {
 		const arr: number[] = [];
 		const result = arr.reduce(removeConsecutiveAdSlotsReducer, []);
-		expect(result).toEqual([]);
+		assert.deepEqual(result, []);
 	});
 });
diff --git a/dotcom-rendering/src/lib/getLiveblogAdPositions.node.test.ts b/dotcom-rendering/src/lib/getLiveblogAdPositions.node.test.ts
new file mode 100644
index 00000000000..9f4d0d69faa
--- /dev/null
+++ b/dotcom-rendering/src/lib/getLiveblogAdPositions.node.test.ts
@@ -0,0 +1,80 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+import { liveBlock as mockBlock } from '../../fixtures/manual/liveBlock';
+import type { Block } from '../types/blocks';
+import { getLiveblogAdPositions } from './getLiveblogAdPositions';
+
+void describe('get liveblog ad positions', () => {
+	const twoBlocks = Array<Block>(2).fill(mockBlock);
+
+	void it('should insert zero ads if zero blocks', () => {
+		assert.deepEqual(getLiveblogAdPositions([]).desktopAdPositions, []);
+		assert.deepEqual(getLiveblogAdPositions([]).mobileAdPositions, []);
+	});
+	void it('should insert zero ads if one block', () => {
+		assert.deepEqual(
+			getLiveblogAdPositions([mockBlock]).desktopAdPositions,
+			[],
+		);
+		assert.deepEqual(
+			getLiveblogAdPositions([mockBlock]).mobileAdPositions,
+			[],
+		);
+	});
+	void it('should insert an ad after the first block if two blocks', () => {
+		assert.deepEqual(
+			getLiveblogAdPositions(twoBlocks).desktopAdPositions,
+			[0],
+		);
+		assert.deepEqual(
+			getLiveblogAdPositions(twoBlocks).mobileAdPositions,
+			[0],
+		);
+	});
+
+	void describe('many blocks', () => {
+		const block: Block = {
+			...mockBlock,
+			elements: [
+				{
+					elementId: '4ac2fcd8-284c-4038-91a1-093811f389ba',
+					_type: 'model.dotcomrendering.pageElements.TextBlockElement',
+					html: `<p>${'a'.repeat(1000)}</p>`,
+				},
+			],
+		};
+
+		const tenBlocks = Array<Block>(10).fill(block);
+
+		void it('On desktop, it should insert an ad after every fourth block given repeated text elements of 1,000 characters', () => {
+			assert.deepEqual(
+				getLiveblogAdPositions(tenBlocks).desktopAdPositions,
+				[0, 4, 8],
+			);
+		});
+
+		void it('On mobile, it should insert an ad after every second block given repeated text elements of 1,000 characters', () => {
+			assert.deepEqual(
+				getLiveblogAdPositions(tenBlocks).mobileAdPositions,
+				[0, 2, 4, 6, 8],
+			);
+		});
+
+		// 40 blocks is enough that without a limit, there would be more than 8 blocks inserted on both mobile and desktop.
+		const fortyBlocks = Array<Block>(40).fill(block);
+
+		void it('On desktop, it should not insert more that 8 slots', () => {
+			assert.equal(
+				getLiveblogAdPositions(fortyBlocks).desktopAdPositions.length,
+				8,
+			);
+		});
+
+		void it('On mobile, it should not insert more that 8 slots', () => {
+			assert.equal(
+				getLiveblogAdPositions(fortyBlocks).mobileAdPositions.length,
+				8,
+			);
+		});
+	});
+});
diff --git a/dotcom-rendering/src/lib/getLiveblogAdPositions.test.ts b/dotcom-rendering/src/lib/getLiveblogAdPositions.test.ts
deleted file mode 100644
index 32d0f203d5d..00000000000
--- a/dotcom-rendering/src/lib/getLiveblogAdPositions.test.ts
+++ /dev/null
@@ -1,70 +0,0 @@
-import { liveBlock as mockBlock } from '../../fixtures/manual/liveBlock';
-import type { Block } from '../types/blocks';
-import { getLiveblogAdPositions } from './getLiveblogAdPositions';
-
-describe('get liveblog ad positions', () => {
-	const twoBlocks = Array<Block>(2).fill(mockBlock);
-
-	it('should insert zero ads if zero blocks', () => {
-		expect(getLiveblogAdPositions([]).desktopAdPositions).toEqual([]);
-		expect(getLiveblogAdPositions([]).mobileAdPositions).toEqual([]);
-	});
-	it('should insert zero ads if one block', () => {
-		expect(getLiveblogAdPositions([mockBlock]).desktopAdPositions).toEqual(
-			[],
-		);
-		expect(getLiveblogAdPositions([mockBlock]).mobileAdPositions).toEqual(
-			[],
-		);
-	});
-	it('should insert an ad after the first block if two blocks', () => {
-		expect(getLiveblogAdPositions(twoBlocks).desktopAdPositions).toEqual([
-			0,
-		]);
-		expect(getLiveblogAdPositions(twoBlocks).mobileAdPositions).toEqual([
-			0,
-		]);
-	});
-
-	describe('many blocks', () => {
-		const block: Block = {
-			...mockBlock,
-			elements: [
-				{
-					elementId: '4ac2fcd8-284c-4038-91a1-093811f389ba',
-					_type: 'model.dotcomrendering.pageElements.TextBlockElement',
-					html: `<p>${'a'.repeat(1000)}</p>`,
-				},
-			],
-		};
-
-		const tenBlocks = Array<Block>(10).fill(block);
-
-		it('On desktop, it should insert an ad after every fourth block given repeated text elements of 1,000 characters', () => {
-			expect(
-				getLiveblogAdPositions(tenBlocks).desktopAdPositions,
-			).toEqual([0, 4, 8]);
-		});
-
-		it('On mobile, it should insert an ad after every second block given repeated text elements of 1,000 characters', () => {
-			expect(getLiveblogAdPositions(tenBlocks).mobileAdPositions).toEqual(
-				[0, 2, 4, 6, 8],
-			);
-		});
-
-		// 40 blocks is enough that without a limit, there would be more than 8 blocks inserted on both mobile and desktop.
-		const fortyBlocks = Array<Block>(40).fill(block);
-
-		it('On desktop, it should not insert more that 8 slots', () => {
-			expect(
-				getLiveblogAdPositions(fortyBlocks).desktopAdPositions,
-			).toHaveLength(8);
-		});
-
-		it('On mobile, it should not insert more that 8 slots', () => {
-			expect(
-				getLiveblogAdPositions(fortyBlocks).mobileAdPositions,
-			).toHaveLength(8);
-		});
-	});
-});
diff --git a/dotcom-rendering/src/lib/getTagPageAdPositions.node.test.ts b/dotcom-rendering/src/lib/getTagPageAdPositions.node.test.ts
new file mode 100644
index 00000000000..c810e9b2346
--- /dev/null
+++ b/dotcom-rendering/src/lib/getTagPageAdPositions.node.test.ts
@@ -0,0 +1,31 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+import { getTagPageBannerAdPositions } from './getTagPageAdPositions';
+
+void describe('Tag page fronts-banner ad slots', () => {
+	void it('should insert 0 ads if there are less than 5 containers', () => {
+		assert.deepEqual(getTagPageBannerAdPositions(1), []);
+		assert.deepEqual(getTagPageBannerAdPositions(3), []);
+	});
+
+	void it('should insert 1 ad if there are 5-7 containers', () => {
+		assert.deepEqual(getTagPageBannerAdPositions(4), [2]);
+		assert.deepEqual(getTagPageBannerAdPositions(6), [2]);
+	});
+
+	void it('should insert 2 ads if there are 8-10 containers', () => {
+		assert.deepEqual(getTagPageBannerAdPositions(7), [2, 5]);
+		assert.deepEqual(getTagPageBannerAdPositions(9), [2, 5]);
+	});
+
+	void it('should insert no more than 8 ads if there are more than 18 containers', () => {
+		assert.deepEqual(
+			getTagPageBannerAdPositions(19),
+			[2, 5, 8, 11, 14, 17],
+		);
+		assert.deepEqual(
+			getTagPageBannerAdPositions(25),
+			[2, 5, 8, 11, 14, 17, 20, 23],
+		);
+	});
+});
diff --git a/dotcom-rendering/src/lib/getTagPageAdPositions.test.ts b/dotcom-rendering/src/lib/getTagPageAdPositions.test.ts
deleted file mode 100644
index 3b743740430..00000000000
--- a/dotcom-rendering/src/lib/getTagPageAdPositions.test.ts
+++ /dev/null
@@ -1,25 +0,0 @@
-import { getTagPageBannerAdPositions } from './getTagPageAdPositions';
-
-describe('Tag page fronts-banner ad slots', () => {
-	it('should insert 0 ads if there are less than 5 containers', () => {
-		expect(getTagPageBannerAdPositions(1)).toEqual([]);
-		expect(getTagPageBannerAdPositions(3)).toEqual([]);
-	});
-
-	it('should insert 1 ad if there are 5-7 containers', () => {
-		expect(getTagPageBannerAdPositions(4)).toEqual([2]);
-		expect(getTagPageBannerAdPositions(6)).toEqual([2]);
-	});
-
-	it('should insert 2 ads if there are 8-10 containers', () => {
-		expect(getTagPageBannerAdPositions(7)).toEqual([2, 5]);
-		expect(getTagPageBannerAdPositions(9)).toEqual([2, 5]);
-	});
-
-	it('should insert no more than 8 ads if there are more than 18 containers', () => {
-		expect(getTagPageBannerAdPositions(19)).toEqual([2, 5, 8, 11, 14, 17]);
-		expect(getTagPageBannerAdPositions(25)).toEqual([
-			2, 5, 8, 11, 14, 17, 20, 23,
-		]);
-	});
-});
diff --git a/dotcom-rendering/src/lib/getZIndex.node.test.ts b/dotcom-rendering/src/lib/getZIndex.node.test.ts
new file mode 100644
index 00000000000..8e30a07ebdd
--- /dev/null
+++ b/dotcom-rendering/src/lib/getZIndex.node.test.ts
@@ -0,0 +1,21 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+import { getZIndex } from './getZIndex';
+
+void describe('getZIndex', () => {
+	void it('gets the correct zindex for group and sibling', () => {
+		assert(getZIndex('sticky-video-button') > getZIndex('sticky-video'));
+		assert(
+			getZIndex('expanded-veggie-menu-wrapper') >
+				getZIndex('expanded-veggie-menu'),
+		);
+		assert(
+			getZIndex('stickyAdWrapperLabsHeader') >
+				getZIndex('stickyAdWrapper'),
+		);
+		assert(getZIndex('tableOfContents') > getZIndex('articleHeadline'));
+		assert(getZIndex('subNavBanner') > getZIndex('articleHeadline'));
+		assert(getZIndex('subNavBanner') > getZIndex('bodyArea'));
+		assert(getZIndex('card-nested-link') > getZIndex('card-link'));
+	});
+});
diff --git a/dotcom-rendering/src/lib/getZIndex.test.ts b/dotcom-rendering/src/lib/getZIndex.test.ts
deleted file mode 100644
index 78bb441772c..00000000000
--- a/dotcom-rendering/src/lib/getZIndex.test.ts
+++ /dev/null
@@ -1,27 +0,0 @@
-import { getZIndex } from './getZIndex';
-
-describe('getZIndex', () => {
-	it('gets the correct zindex for group and sibling', () => {
-		expect(getZIndex('sticky-video-button')).toBeGreaterThan(
-			getZIndex('sticky-video'),
-		);
-		expect(getZIndex('expanded-veggie-menu-wrapper')).toBeGreaterThan(
-			getZIndex('expanded-veggie-menu'),
-		);
-		expect(getZIndex('stickyAdWrapperLabsHeader')).toBeGreaterThan(
-			getZIndex('stickyAdWrapper'),
-		);
-		expect(getZIndex('tableOfContents')).toBeGreaterThan(
-			getZIndex('articleHeadline'),
-		);
-		expect(getZIndex('subNavBanner')).toBeGreaterThan(
-			getZIndex('articleHeadline'),
-		);
-		expect(getZIndex('subNavBanner')).toBeGreaterThan(
-			getZIndex('bodyArea'),
-		);
-		expect(getZIndex('card-nested-link')).toBeGreaterThan(
-			getZIndex('card-link'),
-		);
-	});
-});
diff --git a/dotcom-rendering/src/lib/identity-component-event.node.test.ts b/dotcom-rendering/src/lib/identity-component-event.node.test.ts
new file mode 100644
index 00000000000..6791d7dfcf0
--- /dev/null
+++ b/dotcom-rendering/src/lib/identity-component-event.node.test.ts
@@ -0,0 +1,19 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+import { createAuthenticationEventParams } from './identity-component-event';
+
+void describe('createAuthenticationEventParams', () => {
+	void it('creates authentication event params given a component Id', () => {
+		assert.equal(
+			createAuthenticationEventParams('amp_sidebar_signin'),
+			'componentEventParams=componentType%3Didentityauthentication%26componentId%3Damp_sidebar_signin',
+		);
+	});
+
+	void it('creates authentication event params given a component Id and a page view Id', () => {
+		assert.equal(
+			createAuthenticationEventParams('amp_sidebar_signin', 'pageViewId'),
+			'componentEventParams=componentType%3Didentityauthentication%26componentId%3Damp_sidebar_signin%26viewId%3DpageViewId',
+		);
+	});
+});
diff --git a/dotcom-rendering/src/lib/identity-component-event.test.ts b/dotcom-rendering/src/lib/identity-component-event.test.ts
deleted file mode 100644
index ab697b80550..00000000000
--- a/dotcom-rendering/src/lib/identity-component-event.test.ts
+++ /dev/null
@@ -1,16 +0,0 @@
-import { createAuthenticationEventParams } from './identity-component-event';
-
-describe('createAuthenticationEventParams', () => {
-	it('creates authentication event params given a component Id', () => {
-		expect(createAuthenticationEventParams('amp_sidebar_signin')).toBe(
-			'componentEventParams=componentType%3Didentityauthentication%26componentId%3Damp_sidebar_signin',
-		);
-	});
-	it('creates authentication event params given a component Id and a page view Id', () => {
-		expect(
-			createAuthenticationEventParams('amp_sidebar_signin', 'pageViewId'),
-		).toBe(
-			'componentEventParams=componentType%3Didentityauthentication%26componentId%3Damp_sidebar_signin%26viewId%3DpageViewId',
-		);
-	});
-});
diff --git a/dotcom-rendering/src/lib/isLight.node.test.ts b/dotcom-rendering/src/lib/isLight.node.test.ts
new file mode 100644
index 00000000000..53b7122e902
--- /dev/null
+++ b/dotcom-rendering/src/lib/isLight.node.test.ts
@@ -0,0 +1,45 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+import { isLight } from './isLight';
+
+void describe('isLight', () => {
+	void it('should return the correct response for dark hex colours', () => {
+		for (const colour of [
+			'#791a4e',
+			'#644f4e',
+			'#7f4e2a',
+			'#aa365e',
+			'#5e387c',
+			'#87656e',
+			'#223cdd',
+			'#555eee',
+			'#334cde',
+			'#b54bbb',
+		]) {
+			assert.equal(isLight(colour), false);
+		}
+	});
+
+	void it('should return the correct response for light hex colours', () => {
+		for (const colour of ['#ea3eee', '#97dc45', '#7ec621', '#54dbb6']) {
+			assert.equal(isLight(colour), true);
+		}
+	});
+
+	void it('should return the correct response for 3 digit hex colours', () => {
+		assert.equal(isLight('#f4e'), true);
+		assert.equal(isLight('#fff'), true);
+		assert.equal(isLight('#999'), true);
+		assert.equal(isLight('#64e'), false);
+		assert.equal(isLight('#000'), false);
+	});
+
+	void it('should handle if the # is missing', () => {
+		assert.equal(isLight('97dc45'), true);
+		assert.equal(isLight('000'), false);
+	});
+
+	void it('should handle if the colour string is invalid', () => {
+		assert.equal(isLight('wyx'), false);
+	});
+});
diff --git a/dotcom-rendering/src/lib/isLight.test.ts b/dotcom-rendering/src/lib/isLight.test.ts
deleted file mode 100644
index 4e97490462c..00000000000
--- a/dotcom-rendering/src/lib/isLight.test.ts
+++ /dev/null
@@ -1,40 +0,0 @@
-import { isLight } from './isLight';
-
-describe('isLight', () => {
-	it('should return the correct response for dark hex colours', () => {
-		expect(isLight('#791a4e')).toBe(false);
-		expect(isLight('#644f4e')).toBe(false);
-		expect(isLight('#7f4e2a')).toBe(false);
-		expect(isLight('#aa365e')).toBe(false);
-		expect(isLight('#5e387c')).toBe(false);
-		expect(isLight('#87656e')).toBe(false);
-		expect(isLight('#223cdd')).toBe(false);
-		expect(isLight('#555eee')).toBe(false);
-		expect(isLight('#334cde')).toBe(false);
-		expect(isLight('#b54bbb')).toBe(false);
-	});
-
-	it('should return the correct response for light hex colours', () => {
-		expect(isLight('#ea3eee')).toBe(true);
-		expect(isLight('#97dc45')).toBe(true);
-		expect(isLight('#7ec621')).toBe(true);
-		expect(isLight('#54dbb6')).toBe(true);
-	});
-
-	it('should return the correct response for 3 digit hex colours', () => {
-		expect(isLight('#f4e')).toBe(true);
-		expect(isLight('#fff')).toBe(true);
-		expect(isLight('#999')).toBe(true);
-		expect(isLight('#64e')).toBe(false);
-		expect(isLight('#000')).toBe(false);
-	});
-
-	it('should handle if the # is missing', () => {
-		expect(isLight('97dc45')).toBe(true);
-		expect(isLight('000')).toBe(false);
-	});
-
-	it('should handle if the colour string is invalid', () => {
-		expect(isLight('wyx')).toBe(false);
-	});
-});
diff --git a/dotcom-rendering/src/lib/isValidUrl.node.test.ts b/dotcom-rendering/src/lib/isValidUrl.node.test.ts
new file mode 100644
index 00000000000..b4144202a9f
--- /dev/null
+++ b/dotcom-rendering/src/lib/isValidUrl.node.test.ts
@@ -0,0 +1,35 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+import { isValidUrl } from './isValidUrl';
+
+void describe('isValidUrl', () => {
+	void describe('invalidInputs', () => {
+		const invalidInputs = [
+			'',
+			'guardian.co',
+			'anemailaddress@company.com',
+			'com/hello?athing=1&anotherthing=%20',
+			'https://guardian.co.uk withASpace',
+		];
+
+		for (const input of invalidInputs) {
+			void it(`returns false for invalid input of \`${input}\``, () => {
+				assert.equal(isValidUrl(input), false);
+			});
+		}
+	});
+
+	void describe('validInputs', () => {
+		const validInputs = [
+			'https://guardian.co.uk/australia-news/series/guardian-australia-s-morning-mail',
+			'https://regexr.com/39nr7',
+			'http://www.google.com/hello?athing=1&anotherthing=%20',
+		];
+
+		for (const input of validInputs) {
+			void it(`returns true for valid input of \`${input}\``, () => {
+				assert.equal(isValidUrl(input), true);
+			});
+		}
+	});
+});
diff --git a/dotcom-rendering/src/lib/isValidUrl.test.ts b/dotcom-rendering/src/lib/isValidUrl.test.ts
deleted file mode 100644
index e67eac86dd4..00000000000
--- a/dotcom-rendering/src/lib/isValidUrl.test.ts
+++ /dev/null
@@ -1,35 +0,0 @@
-import { isValidUrl } from './isValidUrl';
-
-describe('isValidUrl', () => {
-	describe('invalidInputs', () => {
-		const invalidInputs = [
-			'',
-			'guardian.co',
-			'anemailaddress@company.com',
-			'com/hello?athing=1&anotherthing=%20',
-			'https://guardian.co.uk withASpace',
-		];
-
-		it.each(invalidInputs)(
-			'returns false for invalid input of `%s`',
-			(input) => {
-				expect(isValidUrl(input)).toBeFalsy();
-			},
-		);
-	});
-
-	describe('validInputs', () => {
-		const validInputs = [
-			'https://guardian.co.uk/australia-news/series/guardian-australia-s-morning-mail',
-			'https://regexr.com/39nr7',
-			'http://www.google.com/hello?athing=1&anotherthing=%20',
-		];
-
-		it.each(validInputs)(
-			'returns true for valid input of `%s`',
-			(input) => {
-				expect(isValidUrl(input)).toBeTruthy();
-			},
-		);
-	});
-});
diff --git a/dotcom-rendering/src/lib/labs.node.test.ts b/dotcom-rendering/src/lib/labs.node.test.ts
new file mode 100644
index 00000000000..e9ff20ca680
--- /dev/null
+++ b/dotcom-rendering/src/lib/labs.node.test.ts
@@ -0,0 +1,36 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+import type { Branding } from '../types/branding';
+import { getOphanComponents } from './labs';
+
+void describe('getOphanComponents', () => {
+	void it('constructs the correct data attributes for branding in article meta', () => {
+		const branding = { sponsorName: 'Some Sponsor' } as Branding;
+		assert.deepEqual(
+			getOphanComponents({
+				branding,
+				locationPrefix: 'article-meta',
+			}),
+			{
+				ophanComponentName: 'labs-logo | article-meta-some-sponsor',
+				ophanComponentLink: 'labs-logo-article-meta-some-sponsor',
+			},
+		);
+	});
+
+	void it('constructs the correct data attributes for branding in related content', () => {
+		const branding = { sponsorName: 'Some Sponsor' } as Branding;
+		assert.deepEqual(
+			getOphanComponents({
+				branding,
+				locationPrefix: 'article-related-content',
+			}),
+			{
+				ophanComponentName:
+					'labs-logo | article-related-content-some-sponsor',
+				ophanComponentLink:
+					'labs-logo-article-related-content-some-sponsor',
+			},
+		);
+	});
+});
diff --git a/dotcom-rendering/src/lib/labs.test.ts b/dotcom-rendering/src/lib/labs.test.ts
deleted file mode 100644
index 178db5e7622..00000000000
--- a/dotcom-rendering/src/lib/labs.test.ts
+++ /dev/null
@@ -1,29 +0,0 @@
-import type { Branding } from '../types/branding';
-import { getOphanComponents } from './labs';
-
-describe('getOphanComponents', () => {
-	it('constructs the correct data attributes for branding in article meta', () => {
-		const branding = { sponsorName: 'Some Sponsor' } as Branding;
-		expect(
-			getOphanComponents({ branding, locationPrefix: 'article-meta' }),
-		).toStrictEqual({
-			ophanComponentName: 'labs-logo | article-meta-some-sponsor',
-			ophanComponentLink: 'labs-logo-article-meta-some-sponsor',
-		});
-	});
-
-	it('constructs the correct data attributes for branding in related content', () => {
-		const branding = { sponsorName: 'Some Sponsor' } as Branding;
-		expect(
-			getOphanComponents({
-				branding,
-				locationPrefix: 'article-related-content',
-			}),
-		).toStrictEqual({
-			ophanComponentName:
-				'labs-logo | article-related-content-some-sponsor',
-			ophanComponentLink:
-				'labs-logo-article-related-content-some-sponsor',
-		});
-	});
-});
diff --git a/dotcom-rendering/src/lib/lang.node.test.ts b/dotcom-rendering/src/lib/lang.node.test.ts
new file mode 100644
index 00000000000..9528912b57f
--- /dev/null
+++ b/dotcom-rendering/src/lib/lang.node.test.ts
@@ -0,0 +1,21 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+import { decideLanguage, decideLanguageDirection } from './lang';
+
+void describe('decideLanguage', () => {
+	void it('returns undefined if input is "en"', () => {
+		assert.equal(decideLanguage('en'), undefined);
+	});
+
+	void it('returns input if it is not "en"', () => {
+		assert.equal(decideLanguage('at'), 'at');
+		assert.equal(decideLanguage('fr'), 'fr');
+	});
+});
+
+void describe('describeLanguageDirection', () => {
+	void it('returns rtl if input is true', () => {
+		assert.equal(decideLanguageDirection(true), 'rtl');
+		assert.equal(decideLanguageDirection(false), undefined);
+	});
+});
diff --git a/dotcom-rendering/src/lib/lang.test.ts b/dotcom-rendering/src/lib/lang.test.ts
deleted file mode 100644
index 42140d1e226..00000000000
--- a/dotcom-rendering/src/lib/lang.test.ts
+++ /dev/null
@@ -1,19 +0,0 @@
-import { decideLanguage, decideLanguageDirection } from './lang';
-
-describe('decideLanguage', () => {
-	test('returns undefined if input is "en"', () => {
-		expect(decideLanguage('en')).toBe(undefined);
-	});
-
-	test('returns input if it is not "en"', () => {
-		expect(decideLanguage('at')).toBe('at');
-		expect(decideLanguage('fr')).toBe('fr');
-	});
-});
-
-describe('describeLanguageDirection', () => {
-	test('returns rtl if input is true', () => {
-		expect(decideLanguageDirection(true)).toBe('rtl');
-		expect(decideLanguageDirection(false)).toBe(undefined);
-	});
-});
diff --git a/dotcom-rendering/src/lib/linkNotificationCount.test.ts b/dotcom-rendering/src/lib/linkNotificationCount.node.test.ts
similarity index 75%
rename from dotcom-rendering/src/lib/linkNotificationCount.test.ts
rename to dotcom-rendering/src/lib/linkNotificationCount.node.test.ts
index 73b30391896..14ef88dc439 100644
--- a/dotcom-rendering/src/lib/linkNotificationCount.test.ts
+++ b/dotcom-rendering/src/lib/linkNotificationCount.node.test.ts
@@ -1,8 +1,10 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import type { DropdownLinkType } from '../components/Dropdown.island';
 import { linkNotificationCount } from './linkNotificationCount';
 
-describe('linksNotificationCount', () => {
-	it('returns the sum of notifications across all links', () => {
+void describe('linksNotificationCount', () => {
+	void it('returns the sum of notifications across all links', () => {
 		const links: DropdownLinkType[] = [
 			{
 				id: 'one',
@@ -40,12 +42,10 @@ describe('linksNotificationCount', () => {
 			},
 		];
 
-		const notificationCount = linkNotificationCount(links);
-
-		expect(notificationCount).toEqual(3);
+		assert.equal(linkNotificationCount(links), 3);
 	});
 
-	it('returns 0 when there are no notifications', () => {
+	void it('returns 0 when there are no notifications', () => {
 		const links = [
 			{
 				id: 'one',
@@ -61,8 +61,6 @@ describe('linksNotificationCount', () => {
 			},
 		];
 
-		const notificationCount = linkNotificationCount(links);
-
-		expect(notificationCount).toEqual(0);
+		assert.equal(linkNotificationCount(links), 0);
 	});
 });
diff --git a/dotcom-rendering/src/lib/liveblogAdSlots.test.ts b/dotcom-rendering/src/lib/liveblogAdSlots.node.test.ts
similarity index 61%
rename from dotcom-rendering/src/lib/liveblogAdSlots.test.ts
rename to dotcom-rendering/src/lib/liveblogAdSlots.node.test.ts
index 99cb32ef8f7..cbc34c58b52 100644
--- a/dotcom-rendering/src/lib/liveblogAdSlots.test.ts
+++ b/dotcom-rendering/src/lib/liveblogAdSlots.node.test.ts
@@ -1,10 +1,12 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import type { FEElement } from '../types/content';
 import {
 	calculateApproximateBlockHeight,
 	shouldDisplayAd,
 } from './liveblogAdSlots';
 
-describe('calculateApproximateBlockHeight', () => {
+void describe('calculateApproximateBlockHeight', () => {
 	const textElementOneLineDesktop: FEElement[] = [
 		{
 			elementId: '1',
@@ -63,85 +65,83 @@ describe('calculateApproximateBlockHeight', () => {
 
 	const defaultBlockSpacing = 75;
 
-	describe('zero elements', () => {
-		it.each(['mobile', 'desktop'])(
-			'should return zero when there are zero elements on %s',
-			(screenSize) => {
+	void describe('zero elements', () => {
+		for (const screenSize of ['mobile', 'desktop']) {
+			void it(`should return zero when there are zero elements on ${screenSize}`, () => {
 				const isMobile = screenSize === 'mobile';
-				expect(calculateApproximateBlockHeight([], isMobile)).toEqual(
+				assert.deepEqual(
+					calculateApproximateBlockHeight([], isMobile),
 					0,
 				);
-			},
-		);
+			});
+		}
 	});
 
-	describe('text block elements', () => {
+	void describe('text block elements', () => {
 		const textLineHeight = 23.8;
 		const margin = 14;
 
-		it.each([
+		for (const [screenSize, textElementOneLine, textElementTwoLines] of [
 			['mobile', textElementOneLineMobile, textElementTwoLinesMobile],
 			['desktop', textElementOneLineDesktop, textElementTwoLinesDestkop],
-		])(
-			'should return the correct height for varying line length on %s',
-			(screenSize, textElementOneLine, textElementTwoLines) => {
+		] as const) {
+			void it(`should return the correct height for varying line length on ${screenSize}`, () => {
 				const isMobile = screenSize === 'mobile';
 
-				expect(
+				assert.deepEqual(
 					calculateApproximateBlockHeight(
 						textElementOneLine,
 						isMobile,
 					),
-				).toEqual(textLineHeight + margin + defaultBlockSpacing);
-				expect(
+					textLineHeight + margin + defaultBlockSpacing,
+				);
+				assert.deepEqual(
 					calculateApproximateBlockHeight(
 						textElementTwoLines,
 						isMobile,
 					),
-				).toEqual(2 * textLineHeight + margin + defaultBlockSpacing);
-			},
-		);
+					2 * textLineHeight + margin + defaultBlockSpacing,
+				);
+			});
+		}
 
-		it.each(['mobile', 'desktop'])(
-			'should return the correct height when there are multiple elements on %s',
-			(screenSize) => {
+		for (const screenSize of ['mobile', 'desktop']) {
+			void it(`should return the correct height when there are multiple elements on ${screenSize}`, () => {
 				const isMobile = screenSize === 'mobile';
 
-				expect(
+				assert.deepEqual(
 					calculateApproximateBlockHeight(
 						multipleTextElements,
 						isMobile,
 					),
-				).toEqual(
 					2 * textLineHeight + 2 * margin + defaultBlockSpacing,
 				);
-			},
-		);
+			});
+		}
 	});
 
-	describe('youtube block elements', () => {
-		it.each([
+	void describe('youtube block elements', () => {
+		for (const [screenSize, heightExcludingText] of [
 			['mobile', 195],
 			['desktop', 350],
-		])(
-			'should return the correct height on %s',
-			(screenSize, heightExcludingText) => {
+		] as const) {
+			void it(`should return the correct height on ${screenSize}`, () => {
 				const isMobile = screenSize === 'mobile';
 				const margin = 12;
 
-				expect(
+				assert.deepEqual(
 					calculateApproximateBlockHeight(youtubeElement, isMobile),
-				).toEqual(heightExcludingText + margin + defaultBlockSpacing);
-			},
-		);
+					heightExcludingText + margin + defaultBlockSpacing,
+				);
+			});
+		}
 	});
 });
 
-describe('shouldDisplayAd', () => {
-	describe('The final block of content', () => {
-		it.each(['mobile', 'desktop'])(
-			'should NOT display an ad if this is the final block on %s',
-			(screenSize) => {
+void describe('shouldDisplayAd', () => {
+	void describe('The final block of content', () => {
+		for (const screenSize of ['mobile', 'desktop']) {
+			void it(`should NOT display an ad if this is the final block on ${screenSize}`, () => {
 				const isMobile = screenSize === 'mobile';
 
 				const block = 5;
@@ -157,15 +157,14 @@ describe('shouldDisplayAd', () => {
 					isMobile,
 				);
 
-				expect(result).toBeFalsy();
-			},
-		);
+				assert(!result);
+			});
+		}
 	});
 
-	describe('Reaching the ad limit', () => {
-		it.each(['mobile', 'desktop'])(
-			'should NOT insert another ad slot if we have reached the limit on %s.',
-			(screenSize) => {
+	void describe('Reaching the ad limit', () => {
+		for (const screenSize of ['mobile', 'desktop']) {
+			void it(`should NOT insert another ad slot if we have reached the limit on ${screenSize}.`, () => {
 				const isMobile = screenSize === 'mobile';
 				const block = 5;
 				const totalBlocks = 10;
@@ -180,15 +179,14 @@ describe('shouldDisplayAd', () => {
 					isMobile,
 				);
 
-				expect(result).toBeFalsy();
-			},
-		);
+				assert(!result);
+			});
+		}
 	});
 
-	describe('inserting the first ad slot', () => {
-		it.each(['mobile', 'desktop'])(
-			'should display ad if this is the first block on %s.',
-			(screenSize) => {
+	void describe('inserting the first ad slot', () => {
+		for (const screenSize of ['mobile', 'desktop']) {
+			void it(`should display ad if this is the first block on ${screenSize}.`, () => {
 				const isMobile = screenSize === 'mobile';
 				const block = 1;
 				const totalBlocks = 10;
@@ -203,18 +201,17 @@ describe('shouldDisplayAd', () => {
 					isMobile,
 				);
 
-				expect(result).toBeTruthy();
-			},
-		);
+				assert(result);
+			});
+		}
 	});
 
-	describe('inserting further ad slots', () => {
-		it.each([
+	void describe('inserting further ad slots', () => {
+		for (const [pixels, screenSize] of [
 			[1200, 'mobile'],
 			[1500, 'desktop'],
-		])(
-			'should display ad if number of pixels without an ad is more than %s on %s',
-			(pixels, screenSize) => {
+		] as const) {
+			void it(`should display ad if number of pixels without an ad is more than ${pixels} on ${screenSize}`, () => {
 				const isMobile = screenSize === 'mobile';
 				const block = 5;
 				const totalBlocks = 10;
@@ -229,16 +226,15 @@ describe('shouldDisplayAd', () => {
 					isMobile,
 				);
 
-				expect(result).toBeTruthy();
-			},
-		);
+				assert(result);
+			});
+		}
 
-		it.each([
+		for (const [pixels, screenSize] of [
 			[1200, 'mobile'],
 			[1500, 'desktop'],
-		])(
-			'should NOT display ad if number of pixels without an ad is less than %s on %s',
-			(pixels, screenSize) => {
+		] as const) {
+			void it(`should NOT display ad if number of pixels without an ad is less than ${pixels} on ${screenSize}`, () => {
 				const isMobile = screenSize === 'mobile';
 				const block = 5;
 				const totalBlocks = 10;
@@ -253,8 +249,8 @@ describe('shouldDisplayAd', () => {
 					isMobile,
 				);
 
-				expect(result).toBeFalsy();
-			},
-		);
+				assert(!result);
+			});
+		}
 	});
 });
diff --git a/dotcom-rendering/src/lib/notification.test.ts b/dotcom-rendering/src/lib/notification.node.test.ts
similarity index 88%
rename from dotcom-rendering/src/lib/notification.test.ts
rename to dotcom-rendering/src/lib/notification.node.test.ts
index cc331b5be59..dea94ec59f0 100644
--- a/dotcom-rendering/src/lib/notification.test.ts
+++ b/dotcom-rendering/src/lib/notification.node.test.ts
@@ -1,7 +1,9 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import { addNotificationsToDropdownLinks } from './notification';
 
-describe('addNotificationsToDropdownLinks', () => {
-	it('augments dropdown links with notifications', () => {
+void describe('addNotificationsToDropdownLinks', () => {
+	void it('augments dropdown links with notifications', () => {
 		const links = [
 			{
 				id: 'account_overview',
@@ -30,7 +32,7 @@ describe('addNotificationsToDropdownLinks', () => {
 			notifications,
 		);
 
-		expect(linksWithNotifications).toEqual([
+		assert.deepEqual(linksWithNotifications, [
 			{
 				id: 'account_overview',
 				url: `https://example.com/account_overview`,
@@ -54,7 +56,7 @@ describe('addNotificationsToDropdownLinks', () => {
 		]);
 	});
 
-	it('adds multiple notification messages to a link', () => {
+	void it('adds multiple notification messages to a link', () => {
 		const links = [
 			{
 				id: 'account_overview',
@@ -83,7 +85,7 @@ describe('addNotificationsToDropdownLinks', () => {
 			notifications,
 		);
 
-		expect(linksWithNotifications).toEqual([
+		assert.deepEqual(linksWithNotifications, [
 			{
 				id: 'account_overview',
 				url: `https://example.com/account_overview`,
@@ -107,7 +109,7 @@ describe('addNotificationsToDropdownLinks', () => {
 		]);
 	});
 
-	it('adds new notifications if target already has notifications', () => {
+	void it('adds new notifications if target already has notifications', () => {
 		const links = [
 			{
 				id: 'account_overview',
@@ -138,7 +140,7 @@ describe('addNotificationsToDropdownLinks', () => {
 			notifications,
 		);
 
-		expect(linksWithNotifications).toEqual([
+		assert.deepEqual(linksWithNotifications, [
 			{
 				id: 'account_overview',
 				url: `https://example.com/account_overview`,
diff --git a/dotcom-rendering/src/lib/ophan-helpers.node.test.ts b/dotcom-rendering/src/lib/ophan-helpers.node.test.ts
new file mode 100644
index 00000000000..b72b33e42c7
--- /dev/null
+++ b/dotcom-rendering/src/lib/ophan-helpers.node.test.ts
@@ -0,0 +1,13 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+import { nestedOphanComponents } from './ophan-helpers';
+
+void describe('Ophan helpers', () => {
+	void it('should handle nested values', () => {
+		assert.equal(nestedOphanComponents('logo'), 'logo');
+		assert.equal(
+			nestedOphanComponents('nav', 'sub nav', 'final element'),
+			'nav : sub nav : final element',
+		);
+	});
+});
diff --git a/dotcom-rendering/src/lib/ophan-helpers.test.ts b/dotcom-rendering/src/lib/ophan-helpers.test.ts
deleted file mode 100644
index e4300fea5cf..00000000000
--- a/dotcom-rendering/src/lib/ophan-helpers.test.ts
+++ /dev/null
@@ -1,10 +0,0 @@
-import { nestedOphanComponents } from './ophan-helpers';
-
-describe('Ophan helpers', () => {
-	it('should handle nested values', () => {
-		expect(nestedOphanComponents('logo')).toBe('logo');
-		expect(nestedOphanComponents('nav', 'sub nav', 'final element')).toBe(
-			'nav : sub nav : final element',
-		);
-	});
-});
diff --git a/dotcom-rendering/src/lib/parser/parseCheckoutOutCookieData.node.test.ts b/dotcom-rendering/src/lib/parser/parseCheckoutOutCookieData.node.test.ts
new file mode 100644
index 00000000000..501886b441f
--- /dev/null
+++ b/dotcom-rendering/src/lib/parser/parseCheckoutOutCookieData.node.test.ts
@@ -0,0 +1,72 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+import { parseCheckoutCompleteCookieData } from './parseCheckoutOutCookieData';
+
+void describe('parseCheckoutCompleteCookieData', () => {
+	const encodeCheckoutCompleteCookieDataObj = (
+		userType: string,
+		product: string,
+	) =>
+		encodeURIComponent(`{"userType":"${userType}","product":"${product}"}`);
+
+	void describe('successful parse', () => {
+		void it('should successfully parse a url encoded json object with a valid userType and product valid field', () => {
+			const cookieString = encodeCheckoutCompleteCookieDataObj(
+				'new',
+				'SupporterPlus',
+			);
+			assert.deepEqual(parseCheckoutCompleteCookieData(cookieString), {
+				userType: 'new',
+				product: 'SupporterPlus',
+			});
+		});
+	});
+
+	void describe('unsuccessful parse should return undefined', () => {
+		void it('invalid user type', () => {
+			const cookieString = encodeCheckoutCompleteCookieDataObj(
+				'invalid',
+				'SupporterPlus',
+			);
+			assert.equal(
+				parseCheckoutCompleteCookieData(cookieString),
+				undefined,
+			);
+		});
+		void it('invalid product type', () => {
+			const cookieString = encodeCheckoutCompleteCookieDataObj(
+				'new',
+				'undefined',
+			);
+			assert.equal(
+				parseCheckoutCompleteCookieData(cookieString),
+				undefined,
+			);
+		});
+		void it('invalid field', () => {
+			const cookieString = encodeURIComponent(
+				`{"invalid":"new", "product": "SupporterPlus"}`,
+			);
+			assert.equal(
+				parseCheckoutCompleteCookieData(cookieString),
+				undefined,
+			);
+		});
+		void it('invalid json structure', () => {
+			const cookieString = encodeURIComponent(
+				`{"userType":"new", "product": "SupporterPlus"`,
+			);
+			assert.equal(
+				parseCheckoutCompleteCookieData(cookieString),
+				undefined,
+			);
+		});
+		void it('plain string', () => {
+			const cookieString = `{"userType":"new", "product": "SupporterPlus"}`;
+			assert.equal(
+				parseCheckoutCompleteCookieData(cookieString),
+				undefined,
+			);
+		});
+	});
+});
diff --git a/dotcom-rendering/src/lib/parser/parseCheckoutOutCookieData.test.ts b/dotcom-rendering/src/lib/parser/parseCheckoutOutCookieData.test.ts
deleted file mode 100644
index e4892e03f16..00000000000
--- a/dotcom-rendering/src/lib/parser/parseCheckoutOutCookieData.test.ts
+++ /dev/null
@@ -1,67 +0,0 @@
-import { parseCheckoutCompleteCookieData } from './parseCheckoutOutCookieData';
-
-describe('parseCheckoutCompleteCookieData', () => {
-	const encodeCheckoutCompleteCookieDataObj = (
-		userType: string,
-		product: string,
-	) =>
-		encodeURIComponent(`{"userType":"${userType}","product":"${product}"}`);
-
-	describe('successful parse', () => {
-		it('should successfully parse a url encoded json object with a valid userType and product valid field', () => {
-			const cookieString = encodeCheckoutCompleteCookieDataObj(
-				'new',
-				'SupporterPlus',
-			);
-			expect(parseCheckoutCompleteCookieData(cookieString)).toStrictEqual(
-				{
-					userType: 'new',
-					product: 'SupporterPlus',
-				},
-			);
-		});
-	});
-
-	describe('unsuccessful parse should return undefined', () => {
-		it('invalid user type', () => {
-			const cookieString = encodeCheckoutCompleteCookieDataObj(
-				'invalid',
-				'SupporterPlus',
-			);
-			expect(parseCheckoutCompleteCookieData(cookieString)).toBe(
-				undefined,
-			);
-		});
-		it('invalid product type', () => {
-			const cookieString = encodeCheckoutCompleteCookieDataObj(
-				'new',
-				'undefined',
-			);
-			expect(parseCheckoutCompleteCookieData(cookieString)).toBe(
-				undefined,
-			);
-		});
-		it('invalid field', () => {
-			const cookieString = encodeURIComponent(
-				`{"invalid":"new", "product": "SupporterPlus"}`,
-			);
-			expect(parseCheckoutCompleteCookieData(cookieString)).toBe(
-				undefined,
-			);
-		});
-		it('invalid json structure', () => {
-			const cookieString = encodeURIComponent(
-				`{"userType":"new", "product": "SupporterPlus"`,
-			);
-			expect(parseCheckoutCompleteCookieData(cookieString)).toBe(
-				undefined,
-			);
-		});
-		it('plain string', () => {
-			const cookieString = `{"userType":"new", "product": "SupporterPlus"}`;
-			expect(parseCheckoutCompleteCookieData(cookieString)).toBe(
-				undefined,
-			);
-		});
-	});
-});
diff --git a/dotcom-rendering/src/lib/puzzlesHubExperiment.node.test.ts b/dotcom-rendering/src/lib/puzzlesHubExperiment.node.test.ts
new file mode 100644
index 00000000000..841fe44f9ea
--- /dev/null
+++ b/dotcom-rendering/src/lib/puzzlesHubExperiment.node.test.ts
@@ -0,0 +1,42 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+import {
+	isPuzzlesHubEnabled,
+	isPuzzlesHubVariant,
+} from './puzzlesHubExperiment';
+
+void describe('isPuzzlesHubVariant', () => {
+	const testCases = [
+		['control', { 'puzzles-new-hub': 'control' }],
+		['missing', {}],
+		['unknown group', { 'puzzles-new-hub': 'other' }],
+		['unrelated participation', { another: 'variant' }],
+	] as const;
+
+	for (const [name, participations] of testCases) {
+		void it(`rejects ${name}`, () => {
+			assert.equal(isPuzzlesHubVariant(participations), false);
+		});
+	}
+
+	void it('accepts only puzzles-new-hub:variant', () => {
+		assert.equal(
+			isPuzzlesHubVariant({ 'puzzles-new-hub': 'variant' }),
+			true,
+		);
+	});
+});
+
+void describe('isPuzzlesHubEnabled', () => {
+	void it('allow local development without an experiment participation', () => {
+		assert.equal(isPuzzlesHubEnabled({}, true), true);
+	});
+
+	void it('requires the variant outside local development', () => {
+		assert.equal(isPuzzlesHubEnabled({}, false), false);
+		assert.equal(
+			isPuzzlesHubEnabled({ 'puzzles-new-hub': 'variant' }, false),
+			true,
+		);
+	});
+});
diff --git a/dotcom-rendering/src/lib/puzzlesHubExperiment.test.ts b/dotcom-rendering/src/lib/puzzlesHubExperiment.test.ts
deleted file mode 100644
index 1a34669908f..00000000000
--- a/dotcom-rendering/src/lib/puzzlesHubExperiment.test.ts
+++ /dev/null
@@ -1,34 +0,0 @@
-import {
-	isPuzzlesHubEnabled,
-	isPuzzlesHubVariant,
-} from './puzzlesHubExperiment';
-
-describe('isPuzzlesHubVariant', () => {
-	it.each([
-		['control', { 'puzzles-new-hub': 'control' }],
-		['missing', {}],
-		['unknown group', { 'puzzles-new-hub': 'other' }],
-		['unrelated participation', { another: 'variant' }],
-	])('rejects %s', (_, participations) => {
-		expect(isPuzzlesHubVariant(participations)).toBe(false);
-	});
-
-	it('accepts only puzzles-new-hub:variant', () => {
-		expect(isPuzzlesHubVariant({ 'puzzles-new-hub': 'variant' })).toBe(
-			true,
-		);
-	});
-});
-
-describe('isPuzzlesHubEnabled', () => {
-	it('allow local development without an experiment participation', () => {
-		expect(isPuzzlesHubEnabled({}, true)).toBe(true);
-	});
-
-	it('requires the variant outside local development', () => {
-		expect(isPuzzlesHubEnabled({}, false)).toBe(false);
-		expect(
-			isPuzzlesHubEnabled({ 'puzzles-new-hub': 'variant' }, false),
-		).toBe(true);
-	});
-});
diff --git a/dotcom-rendering/src/lib/querystring.test.ts b/dotcom-rendering/src/lib/querystring.node.test.ts
similarity index 62%
rename from dotcom-rendering/src/lib/querystring.test.ts
rename to dotcom-rendering/src/lib/querystring.node.test.ts
index cecfd9f2b3d..d243fb85183 100644
--- a/dotcom-rendering/src/lib/querystring.test.ts
+++ b/dotcom-rendering/src/lib/querystring.node.test.ts
@@ -1,7 +1,9 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import { constructQuery } from './querystring';
 
-describe('constructQuery', () => {
-	it('constructs the correct query string from an object', () => {
+void describe('constructQuery', () => {
+	void it('constructs the correct query string from an object', () => {
 		const testParams = {
 			sens: 'f',
 			si: 'f',
@@ -16,6 +18,6 @@ describe('constructQuery', () => {
 			a: undefined,
 		};
 		const expectedQuery = `sens=f&si=f&vl=333&cc=UK&s=sport&inskin=f&ct=article&url=%2Fsport%2F2017%2Fsep%2F30%2Ftest-article&su=0&pa=f&a=undefined`;
-		expect(constructQuery(testParams)).toBe(expectedQuery);
+		assert.equal(constructQuery(testParams), expectedQuery);
 	});
 });
diff --git a/dotcom-rendering/src/lib/result.node.test.ts b/dotcom-rendering/src/lib/result.node.test.ts
new file mode 100644
index 00000000000..dc8e9269cf8
--- /dev/null
+++ b/dotcom-rendering/src/lib/result.node.test.ts
@@ -0,0 +1,193 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+import { literal, safeParse } from 'valibot';
+import { error, fromValibot, ok, type Result } from './result';
+
+void describe('ok', () => {
+	void it('creates an instance of Ok', () => {
+		const result = ok(3);
+		const value = result.getOrThrow('Expected an Ok');
+
+		assert.equal(result.ok, true);
+		assert.equal(value, 3);
+	});
+});
+
+void describe('error', () => {
+	void it('creates an instance of Err', () => {
+		const result = error('An error');
+		const err = result.getErrorOrThrow('Expected an Err');
+
+		assert.equal(result.ok, false);
+		assert.equal(err, 'An error');
+	});
+});
+
+void describe('flatMap', () => {
+	const f = (a: number): Result<unknown, number> => ok(a + 1);
+	const h = (): Result<string, number> => error('h error');
+
+	void it('runs the function and unwraps the result when both Results are Ok', () => {
+		const result = ok(3).flatMap(f);
+		const value = result.getOrThrow('Expected an Ok');
+
+		assert.equal(result.ok, true);
+		assert.equal(value, 4);
+	});
+
+	void it('passes through the Err when the first Result is Err', () => {
+		const result = error<string, number>('error message').flatMap(f);
+		const err = result.getErrorOrThrow('Expected an Err');
+
+		assert.equal(result.ok, false);
+		assert.equal(err, 'error message');
+	});
+
+	void it('passes through the Err when the second Result is Err', () => {
+		const result = ok(3).flatMap(h);
+		const err = result.getErrorOrThrow('Expected an Err');
+
+		assert.equal(result.ok, false);
+		assert.equal(err, 'h error');
+	});
+
+	void it('passes through the first Err when both are Err', () => {
+		const result = error<string, number>('error message').flatMap(h);
+		const err = result.getErrorOrThrow('Expected an Err');
+
+		assert.equal(result.ok, false);
+		assert.equal(err, 'error message');
+	});
+
+	void it('obeys left identity law', () => {
+		const value = 3;
+
+		assert.deepEqual(ok(value).flatMap(f), f(value));
+	});
+
+	void it('obeys right identity law', () => {
+		const result = ok(3);
+
+		assert.deepEqual(result.flatMap(ok), result);
+	});
+
+	void it('obeys associativity law', () => {
+		const result = ok(3);
+		const g = (a: number): Result<unknown, number> => ok(a * 3);
+
+		assert.deepEqual(
+			result.flatMap(f).flatMap(g),
+			result.flatMap((a) => f(a).flatMap(g)),
+		);
+	});
+});
+
+void describe('map', () => {
+	const f = (a: number): number => a + 1;
+
+	void it('runs the function when Result is Ok', () => {
+		const result = ok(3).map(f);
+		const value = result.getOrThrow('Expected an Ok');
+
+		assert.equal(result.ok, true);
+		assert.equal(value, 4);
+	});
+
+	void it('passes the error through when Result is Err', () => {
+		const result = error<string, number>('error message').map(f);
+		const err = result.getErrorOrThrow('Expected an Err');
+
+		assert.equal(result.ok, false);
+		assert.equal(err, 'error message');
+	});
+
+	void it('obeys identity', () => {
+		const identity = <A>(a: A): A => a;
+		const value = 3;
+		const result = ok(value);
+
+		assert.deepEqual(result.map(identity), result);
+	});
+
+	void it('obeys composition', () => {
+		const g = (a: number): number => a * 3;
+		const result = ok(3);
+
+		assert.deepEqual(
+			result.map(f).map(g),
+			result.map((a) => g(f(a))),
+		);
+	});
+});
+
+void describe('mapError', () => {
+	const f = (err: string): string => `An error: ${err}`;
+
+	void it('produces a new error if Err', () => {
+		const err = error('error details');
+
+		assert.deepEqual(err.mapError(f), error('An error: error details'));
+	});
+
+	void it('does nothing if Ok', () => {
+		const result = ok<string, number>(3);
+
+		assert.deepEqual(result.mapError(f), result);
+	});
+});
+
+void describe('getOrThrow', () => {
+	void it('gets the value if Ok', () => {
+		const value = ok(3).getOrThrow('Expected an Ok');
+
+		assert.equal(value, 3);
+	});
+
+	void it('throws if Err', () => {
+		const result = error('An error');
+
+		assert.throws(
+			() => result.getOrThrow('Expected an Ok'),
+			/Expected an Ok/,
+		);
+	});
+});
+
+void describe('getErrorOrThrow', () => {
+	void it('gets the value if Err', () => {
+		const err = error('An error').getErrorOrThrow('Expected an Err');
+
+		assert.equal(err, 'An error');
+	});
+
+	void it('throws if Ok', () => {
+		const result = ok(3);
+
+		assert.throws(
+			() => result.getErrorOrThrow('Expected an Err'),
+			/Expected an Err/,
+		);
+	});
+});
+
+void describe('fromValibot', () => {
+	const schema = literal('string literal');
+
+	void it('creates an Ok from a successful parse result', () => {
+		const valibotResult = safeParse(schema, 'string literal');
+
+		const result = fromValibot(valibotResult);
+		const value = result.getOrThrow('Expected an Ok');
+
+		assert.equal(value, 'string literal');
+	});
+
+	void it('creates an Err from an unsuccessful parse result', () => {
+		const valibotResult = safeParse(schema, 'invalid literal');
+
+		const result = fromValibot(valibotResult);
+		const err = result.getErrorOrThrow('Expected an Err');
+
+		assert.equal(err[0].expected, '"string literal"');
+	});
+});
diff --git a/dotcom-rendering/src/lib/result.test.ts b/dotcom-rendering/src/lib/result.test.ts
deleted file mode 100644
index b625fc5e213..00000000000
--- a/dotcom-rendering/src/lib/result.test.ts
+++ /dev/null
@@ -1,185 +0,0 @@
-import { literal, safeParse } from 'valibot';
-import { error, fromValibot, ok, type Result } from './result';
-
-describe('ok', () => {
-	it('creates an instance of Ok', () => {
-		const result = ok(3);
-		const value = result.getOrThrow('Expected an Ok');
-
-		expect(result.ok).toBe(true);
-		expect(value).toBe(3);
-	});
-});
-
-describe('error', () => {
-	it('creates an instance of Err', () => {
-		const result = error('An error');
-		const err = result.getErrorOrThrow('Expected an Err');
-
-		expect(result.ok).toBe(false);
-		expect(err).toBe('An error');
-	});
-});
-
-describe('flatMap', () => {
-	const f = (a: number): Result<unknown, number> => ok(a + 1);
-	const h = (): Result<string, number> => error('h error');
-
-	it('runs the function and unwraps the result when both Results are Ok', () => {
-		const result = ok(3).flatMap(f);
-		const value = result.getOrThrow('Expected an Ok');
-
-		expect(result.ok).toBe(true);
-		expect(value).toBe(4);
-	});
-
-	it('passes through the Err when the first Result is Err', () => {
-		const result = error<string, number>('error message').flatMap(f);
-		const err = result.getErrorOrThrow('Expected an Err');
-
-		expect(result.ok).toBe(false);
-		expect(err).toBe('error message');
-	});
-
-	it('passes through the Err when the second Result is Err', () => {
-		const result = ok(3).flatMap(h);
-		const err = result.getErrorOrThrow('Expected an Err');
-
-		expect(result.ok).toBe(false);
-		expect(err).toBe('h error');
-	});
-
-	it('passes through the first Err when both are Err', () => {
-		const result = error<string, number>('error message').flatMap(h);
-		const err = result.getErrorOrThrow('Expected an Err');
-
-		expect(result.ok).toBe(false);
-		expect(err).toBe('error message');
-	});
-
-	it('obeys left identity law', () => {
-		const value = 3;
-
-		expect(ok(value).flatMap(f)).toEqual(f(value));
-	});
-
-	it('obeys right identity law', () => {
-		const result = ok(3);
-
-		expect(result.flatMap(ok)).toEqual(result);
-	});
-
-	it('obeys associativity law', () => {
-		const result = ok(3);
-		const g = (a: number): Result<unknown, number> => ok(a * 3);
-
-		expect(result.flatMap(f).flatMap(g)).toEqual(
-			result.flatMap((a) => f(a).flatMap(g)),
-		);
-	});
-});
-
-describe('map', () => {
-	const f = (a: number): number => a + 1;
-
-	it('runs the function when Result is Ok', () => {
-		const result = ok(3).map(f);
-		const value = result.getOrThrow('Expected an Ok');
-
-		expect(result.ok).toBe(true);
-		expect(value).toBe(4);
-	});
-
-	it('passes the error through when Result is Err', () => {
-		const result = error<string, number>('error message').map(f);
-		const err = result.getErrorOrThrow('Expected an Err');
-
-		expect(result.ok).toBe(false);
-		expect(err).toBe('error message');
-	});
-
-	it('obeys identity', () => {
-		const identity = <A>(a: A): A => a;
-		const value = 3;
-		const result = ok(value);
-
-		expect(result.map(identity)).toEqual(result);
-	});
-
-	it('obeys composition', () => {
-		const g = (a: number): number => a * 3;
-		const result = ok(3);
-
-		expect(result.map(f).map(g)).toEqual(result.map((a) => g(f(a))));
-	});
-});
-
-describe('mapError', () => {
-	const f = (e: string): string => `An error: ${e}`;
-
-	it('produces a new error if Err', () => {
-		const err = error('error details');
-
-		expect(err.mapError(f)).toEqual(error('An error: error details'));
-	});
-
-	it('does nothing if Ok', () => {
-		const result = ok<string, number>(3);
-
-		expect(result.mapError(f)).toEqual(result);
-	});
-});
-
-describe('getOrThrow', () => {
-	it('gets the value if Ok', () => {
-		const value = ok(3).getOrThrow('Expected an Ok');
-
-		expect(value).toBe(3);
-	});
-
-	it('throws if Err', () => {
-		const result = error('An error');
-
-		expect(() => result.getOrThrow('Expected an Ok')).toThrow(
-			'Expected an Ok',
-		);
-	});
-});
-
-describe('getErrorOrThrow', () => {
-	it('gets the value if Err', () => {
-		const err = error('An error').getErrorOrThrow('Expected an Err');
-
-		expect(err).toBe('An error');
-	});
-
-	it('throws if Ok', () => {
-		const result = ok(3);
-
-		expect(() => result.getErrorOrThrow('Expected an Err')).toThrow(
-			'Expected an Err',
-		);
-	});
-});
-
-describe('fromValibot', () => {
-	const schema = literal('string literal');
-
-	it('creates an Ok from a successful parse result', () => {
-		const valibotResult = safeParse(schema, 'string literal');
-
-		const result = fromValibot(valibotResult);
-		const value = result.getOrThrow('Expected an Ok');
-
-		expect(value).toBe('string literal');
-	});
-
-	it('creates an Err from an unsuccessful parse result', () => {
-		const valibotResult = safeParse(schema, 'invalid literal');
-
-		const result = fromValibot(valibotResult);
-		const err = result.getErrorOrThrow('Expected an Err');
-
-		expect(err[0].expected).toBe('"string literal"');
-	});
-});
diff --git a/dotcom-rendering/src/lib/sendTargetingParams.apps.test.ts b/dotcom-rendering/src/lib/sendTargetingParams.apps.node.test.ts
similarity index 79%
rename from dotcom-rendering/src/lib/sendTargetingParams.apps.test.ts
rename to dotcom-rendering/src/lib/sendTargetingParams.apps.node.test.ts
index 83eb9e5a2b1..7adcf443677 100644
--- a/dotcom-rendering/src/lib/sendTargetingParams.apps.test.ts
+++ b/dotcom-rendering/src/lib/sendTargetingParams.apps.node.test.ts
@@ -1,7 +1,9 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import { getTargetingParams } from './sendTargetingParams.apps';
 
-describe('getTargetingParams', () => {
-	it('extracts ad targeting params from editionCommercialProperties in the format Bridget consumes', () => {
+void describe('getTargetingParams', () => {
+	void it('extracts ad targeting params from editionCommercialProperties in the format Bridget consumes', () => {
 		const testEditionCommercialProperties = {
 			adTargeting: [
 				{
@@ -64,7 +66,8 @@ describe('getTargetingParams', () => {
 			['k', 'us-politics,state-of-georgia,us-crime,us-news,donaldtrump'],
 		]);
 
-		expect(getTargetingParams(testEditionCommercialProperties)).toEqual(
+		assert.deepEqual(
+			getTargetingParams(testEditionCommercialProperties),
 			expectedValue,
 		);
 	});
diff --git a/dotcom-rendering/src/lib/theFilter.node.test.ts b/dotcom-rendering/src/lib/theFilter.node.test.ts
new file mode 100644
index 00000000000..d30986f96f6
--- /dev/null
+++ b/dotcom-rendering/src/lib/theFilter.node.test.ts
@@ -0,0 +1,37 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+import { isFilterPageId } from './theFilter';
+
+void describe('isFilterPageId', () => {
+	void it('returns true for a UK Filter article pageId', () => {
+		assert.equal(
+			isFilterPageId(
+				'thefilter/2026/jul/02/jess-cartner-morleys-july-style-essentials-2026',
+			),
+			true,
+		);
+	});
+
+	void it('returns true for a US Filter article pageId', () => {
+		assert.equal(
+			isFilterPageId(
+				'thefilter-us/2025/dec/27/best-wine-subscriptions-us',
+			),
+			true,
+		);
+	});
+
+	void it('returns false for a non-Filter pageId', () => {
+		assert.equal(
+			isFilterPageId('technology/2026/jan/01/some-other-article'),
+			false,
+		);
+	});
+
+	void it('returns false for a pageId that merely contains "thefilter" mid-string', () => {
+		assert.equal(
+			isFilterPageId('lifestyle/thefilter-mentioned/some-article'),
+			false,
+		);
+	});
+});
diff --git a/dotcom-rendering/src/lib/theFilter.test.ts b/dotcom-rendering/src/lib/theFilter.test.ts
deleted file mode 100644
index bc2723ddaf4..00000000000
--- a/dotcom-rendering/src/lib/theFilter.test.ts
+++ /dev/null
@@ -1,31 +0,0 @@
-import { isFilterPageId } from './theFilter';
-
-describe('isFilterPageId', () => {
-	it('returns true for a UK Filter article pageId', () => {
-		expect(
-			isFilterPageId(
-				'thefilter/2026/jul/02/jess-cartner-morleys-july-style-essentials-2026',
-			),
-		).toBe(true);
-	});
-
-	it('returns true for a US Filter article pageId', () => {
-		expect(
-			isFilterPageId(
-				'thefilter-us/2025/dec/27/best-wine-subscriptions-us',
-			),
-		).toBe(true);
-	});
-
-	it('returns false for a non-Filter pageId', () => {
-		expect(
-			isFilterPageId('technology/2026/jan/01/some-other-article'),
-		).toBe(false);
-	});
-
-	it('returns false for a pageId that merely contains "thefilter" mid-string', () => {
-		expect(
-			isFilterPageId('lifestyle/thefilter-mentioned/some-article'),
-		).toBe(false);
-	});
-});
diff --git a/dotcom-rendering/src/lib/transparentColour.node.test.ts b/dotcom-rendering/src/lib/transparentColour.node.test.ts
new file mode 100644
index 00000000000..0f0049786de
--- /dev/null
+++ b/dotcom-rendering/src/lib/transparentColour.node.test.ts
@@ -0,0 +1,46 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+import { transparentColour } from './transparentColour';
+
+void describe('transparentColour', () => {
+	const validHexColours = [
+		['#000000', 'rgba(0, 0, 0, 0.5)'],
+		['#C70000', 'rgba(199, 0, 0, 0.5)'],
+		['#aabbcc', 'rgba(170, 187, 204, 0.5)'],
+		['#ffffff', 'rgba(255, 255, 255, 0.5)'],
+	] as const;
+
+	for (const [hex, output] of validHexColours) {
+		void it(`For valid hex ${hex}, return ${output}`, () => {
+			assert.equal(transparentColour(hex), output);
+		});
+	}
+
+	const shortHexColours = [
+		['#000', 'rgba(0, 0, 0, 0.5)'],
+		['#c00', 'rgba(204, 0, 0, 0.5)'],
+		['#abc', 'rgba(170, 187, 204, 0.5)'],
+		['#fff', 'rgba(255, 255, 255, 0.5)'],
+	] as const;
+
+	for (const [hex, output] of shortHexColours) {
+		void it(`For short hex ${hex}, return ${output}`, () => {
+			assert.equal(transparentColour(hex), output);
+		});
+	}
+
+	const invalidHexColours = [
+		'---',
+		'#ab',
+		'#abcd',
+		'#gggggg',
+		'-ffffff',
+		'rgb(0,0,0)',
+	];
+
+	for (const hex of invalidHexColours) {
+		void it(`For invalid hex ${hex}, return rgba(127, 127, 127, 0.5)`, () => {
+			assert.equal(transparentColour(hex), 'rgba(127, 127, 127, 0.5)');
+		});
+	}
+});
diff --git a/dotcom-rendering/src/lib/transparentColour.test.ts b/dotcom-rendering/src/lib/transparentColour.test.ts
deleted file mode 100644
index 8cb10e6be48..00000000000
--- a/dotcom-rendering/src/lib/transparentColour.test.ts
+++ /dev/null
@@ -1,28 +0,0 @@
-import { transparentColour } from './transparentColour';
-
-describe('transparentColour', () => {
-	test.each([
-		['#000000', 'rgba(0, 0, 0, 0.5)'],
-		['#C70000', 'rgba(199, 0, 0, 0.5)'],
-		['#aabbcc', 'rgba(170, 187, 204, 0.5)'],
-		['#ffffff', 'rgba(255, 255, 255, 0.5)'],
-	])('For valid hex %s, return %s', (hex, output) => {
-		expect(transparentColour(hex)).toEqual(output);
-	});
-
-	test.each([
-		['#000', 'rgba(0, 0, 0, 0.5)'],
-		['#c00', 'rgba(204, 0, 0, 0.5)'],
-		['#abc', 'rgba(170, 187, 204, 0.5)'],
-		['#fff', 'rgba(255, 255, 255, 0.5)'],
-	])('For short hex %s, return %s', (hex, output) => {
-		expect(transparentColour(hex)).toEqual(output);
-	});
-
-	test.each(['---', '#ab', '#abcd', '#gggggg', '-ffffff', 'rgb(0,0,0)'])(
-		'For invalid hex %s, return rgba(127, 127, 127, 0.5)',
-		(hex) => {
-			expect(transparentColour(hex)).toEqual('rgba(127, 127, 127, 0.5)');
-		},
-	);
-});
diff --git a/dotcom-rendering/src/lib/tuple.node.test.ts b/dotcom-rendering/src/lib/tuple.node.test.ts
new file mode 100644
index 00000000000..f15ef9c3a9f
--- /dev/null
+++ b/dotcom-rendering/src/lib/tuple.node.test.ts
@@ -0,0 +1,63 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+import { isNonEmptyArray, takeFirst } from './tuple';
+
+void describe('takeFirst', () => {
+	void it('Always returns the correct array length when the array is one less, the same as, or one more than n', () => {
+		const results = [
+			// Format, from 1 to 12, cover length n - 1, n & n+1
+			takeFirst([0, 1], 1),
+			takeFirst([0], 1),
+			takeFirst([], 1),
+			takeFirst([0, 1, 2], 2),
+			takeFirst([0, 1], 2),
+			takeFirst([0], 2),
+			takeFirst([0, 1, 2, 3], 3),
+			takeFirst([0, 1, 2], 3),
+			takeFirst([0, 1], 3),
+			takeFirst([0, 1, 2, 3, 4], 4),
+			takeFirst([0, 1, 2, 3], 4),
+			takeFirst([0, 1, 2], 4),
+			takeFirst([0, 1, 2, 3, 4, 5], 5),
+			takeFirst([0, 1, 2, 3, 4], 5),
+			takeFirst([0, 1, 2, 3], 5),
+			takeFirst([0, 1, 2, 3, 4, 5, 6], 6),
+			takeFirst([0, 1, 2, 3, 4, 5], 6),
+			takeFirst([0, 1, 2, 3, 4], 6),
+			takeFirst([0, 1, 2, 3, 4, 5, 6, 7], 7),
+			takeFirst([0, 1, 2, 3, 4, 5, 6], 7),
+			takeFirst([0, 1, 2, 3, 4, 5], 7),
+			takeFirst([0, 1, 2, 3, 4, 5, 6, 7, 8], 8),
+			takeFirst([0, 1, 2, 3, 4, 5, 6, 7], 8),
+			takeFirst([0, 1, 2, 3, 4, 5, 6], 8),
+			takeFirst([0, 1, 2, 3, 4, 5, 6, 7, 8, 9], 9),
+			takeFirst([0, 1, 2, 3, 4, 5, 6, 7, 8], 9),
+			takeFirst([0, 1, 2, 3, 4, 5, 6, 7], 9),
+			takeFirst([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10], 10),
+			takeFirst([0, 1, 2, 3, 4, 5, 6, 7, 8, 9], 10),
+			takeFirst([0, 1, 2, 3, 4, 5, 6, 7, 8], 10),
+			takeFirst([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11], 11),
+			takeFirst([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10], 11),
+			takeFirst([0, 1, 2, 3, 4, 5, 6, 7, 8, 9], 11),
+			takeFirst([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12], 12),
+			takeFirst([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11], 12),
+			takeFirst([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10], 12),
+		] as const;
+
+		const expectedLengths = [
+			1, 1, 0, 2, 2, 1, 3, 3, 2, 4, 4, 3, 5, 5, 4, 6, 6, 5, 7, 7, 6, 8, 8,
+			7, 9, 9, 8, 10, 10, 9, 11, 11, 10, 12, 12, 11,
+		];
+
+		assert.deepEqual(
+			results.map((result) => result.length),
+			expectedLengths,
+		);
+	});
+});
+
+void it('isNonEmptyArray', () => {
+	assert.equal(isNonEmptyArray([]), false);
+	assert.equal(isNonEmptyArray([1]), true);
+	assert.equal(isNonEmptyArray([1, 2, 3]), true);
+});
diff --git a/dotcom-rendering/src/lib/tuple.test.ts b/dotcom-rendering/src/lib/tuple.test.ts
deleted file mode 100644
index 33b398afb3d..00000000000
--- a/dotcom-rendering/src/lib/tuple.test.ts
+++ /dev/null
@@ -1,89 +0,0 @@
-import { isNonEmptyArray, takeFirst } from './tuple';
-
-describe('takeFirst', () => {
-	it('Always returns the correct array length when the array is one less, the same as, or one more than n', () => {
-		const results = [
-			// Format, from 1 to 12, cover length n - 1, n & n+1
-			takeFirst([0, 1], 1),
-			takeFirst([0], 1),
-			takeFirst([], 1),
-			takeFirst([0, 1, 2], 2),
-			takeFirst([0, 1], 2),
-			takeFirst([0], 2),
-			takeFirst([0, 1, 2, 3], 3),
-			takeFirst([0, 1, 2], 3),
-			takeFirst([0, 1], 3),
-			takeFirst([0, 1, 2, 3, 4], 4),
-			takeFirst([0, 1, 2, 3], 4),
-			takeFirst([0, 1, 2], 4),
-			takeFirst([0, 1, 2, 3, 4, 5], 5),
-			takeFirst([0, 1, 2, 3, 4], 5),
-			takeFirst([0, 1, 2, 3], 5),
-			takeFirst([0, 1, 2, 3, 4, 5, 6], 6),
-			takeFirst([0, 1, 2, 3, 4, 5], 6),
-			takeFirst([0, 1, 2, 3, 4], 6),
-			takeFirst([0, 1, 2, 3, 4, 5, 6, 7], 7),
-			takeFirst([0, 1, 2, 3, 4, 5, 6], 7),
-			takeFirst([0, 1, 2, 3, 4, 5], 7),
-			takeFirst([0, 1, 2, 3, 4, 5, 6, 7, 8], 8),
-			takeFirst([0, 1, 2, 3, 4, 5, 6, 7], 8),
-			takeFirst([0, 1, 2, 3, 4, 5, 6], 8),
-			takeFirst([0, 1, 2, 3, 4, 5, 6, 7, 8, 9], 9),
-			takeFirst([0, 1, 2, 3, 4, 5, 6, 7, 8], 9),
-			takeFirst([0, 1, 2, 3, 4, 5, 6, 7], 9),
-			takeFirst([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10], 10),
-			takeFirst([0, 1, 2, 3, 4, 5, 6, 7, 8, 9], 10),
-			takeFirst([0, 1, 2, 3, 4, 5, 6, 7, 8], 10),
-			takeFirst([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11], 11),
-			takeFirst([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10], 11),
-			takeFirst([0, 1, 2, 3, 4, 5, 6, 7, 8, 9], 11),
-			takeFirst([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12], 12),
-			takeFirst([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11], 12),
-			takeFirst([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10], 12),
-		] as const;
-
-		// Expected results from n are n, n & n-1
-		expect(results[0].length).toEqual(1);
-		expect(results[1].length).toEqual(1);
-		expect(results[2].length).toEqual(0);
-		expect(results[3].length).toEqual(2);
-		expect(results[4].length).toEqual(2);
-		expect(results[5].length).toEqual(1);
-		expect(results[6].length).toEqual(3);
-		expect(results[7].length).toEqual(3);
-		expect(results[8].length).toEqual(2);
-		expect(results[9].length).toEqual(4);
-		expect(results[10].length).toEqual(4);
-		expect(results[11].length).toEqual(3);
-		expect(results[12].length).toEqual(5);
-		expect(results[13].length).toEqual(5);
-		expect(results[14].length).toEqual(4);
-		expect(results[15].length).toEqual(6);
-		expect(results[16].length).toEqual(6);
-		expect(results[17].length).toEqual(5);
-		expect(results[18].length).toEqual(7);
-		expect(results[19].length).toEqual(7);
-		expect(results[20].length).toEqual(6);
-		expect(results[21].length).toEqual(8);
-		expect(results[22].length).toEqual(8);
-		expect(results[23].length).toEqual(7);
-		expect(results[24].length).toEqual(9);
-		expect(results[25].length).toEqual(9);
-		expect(results[26].length).toEqual(8);
-		expect(results[27].length).toEqual(10);
-		expect(results[28].length).toEqual(10);
-		expect(results[29].length).toEqual(9);
-		expect(results[30].length).toEqual(11);
-		expect(results[31].length).toEqual(11);
-		expect(results[32].length).toEqual(10);
-		expect(results[33].length).toEqual(12);
-		expect(results[34].length).toEqual(12);
-		expect(results[35].length).toEqual(11);
-	});
-});
-
-it('isNonEmptyArray', () => {
-	expect(isNonEmptyArray([])).toBe(false);
-	expect(isNonEmptyArray([1])).toBe(true);
-	expect(isNonEmptyArray([1, 2, 3])).toBe(true);
-});
diff --git a/dotcom-rendering/src/lib/video.test.ts b/dotcom-rendering/src/lib/video.node.test.ts
similarity index 60%
rename from dotcom-rendering/src/lib/video.test.ts
rename to dotcom-rendering/src/lib/video.node.test.ts
index ac23ac49b5f..9fd51331b8c 100644
--- a/dotcom-rendering/src/lib/video.test.ts
+++ b/dotcom-rendering/src/lib/video.node.test.ts
@@ -1,3 +1,5 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import type { FEMediaAsset } from '../frontend/feFront';
 import type { VideoAssets } from '../types/content';
 import type { Source } from './video';
@@ -88,18 +90,19 @@ const m3u8Src720h: Source = {
 	hasAudio: true,
 };
 
-describe('video', () => {
-	describe('extractValidSourcesFromAssets', () => {
-		it('should drop unsupported assets', () => {
+void describe('video', () => {
+	void describe('extractValidSourcesFromAssets', () => {
+		void it('should drop unsupported assets', () => {
 			const assets = [mp4Asset480w, m3u8Asset720h, unsupportedAsset];
 			const expected = [mp4Src480w, m3u8Src720h];
 
-			expect(extractValidSourcesFromAssets(assets, 'Loop')).toEqual(
+			assert.deepEqual(
+				extractValidSourcesFromAssets(assets, 'Loop'),
 				expected,
 			);
 		});
 
-		it('should reorder sources by supportedVideoFileTypes order', () => {
+		void it('should reorder sources by supportedVideoFileTypes order', () => {
 			const assets = [
 				m3u8Asset720h,
 				mp4Asset480w,
@@ -114,49 +117,54 @@ describe('video', () => {
 				m3u8Src720h,
 				m3u8Src720h,
 			];
-			expect(extractValidSourcesFromAssets(assets, 'Loop')).toEqual(
+			assert.deepEqual(
+				extractValidSourcesFromAssets(assets, 'Loop'),
 				expected,
 			);
 		});
 
-		it('should prefer M3U8 sources for long videos with Default video style', () => {
+		void it('should prefer M3U8 sources for long videos with Default video style', () => {
 			const assets = [mp4Asset480w, m3u8Asset720h, mp4Asset720h];
 			const expected = [m3u8Src720h, mp4Src480w, mp4Src720h];
 
-			expect(
+			assert.deepEqual(
 				extractValidSourcesFromAssets(assets, 'Default', 37),
-			).toEqual(expected);
+				expected,
+			);
 		});
 
-		it('should prefer MP4 sources for short videos with Default video style', () => {
+		void it('should prefer MP4 sources for short videos with Default video style', () => {
 			const assets = [mp4Asset480w, m3u8Asset720h, mp4Asset720h];
 			const expected = [mp4Src480w, mp4Src720h, m3u8Src720h];
 
-			expect(
+			assert.deepEqual(
 				extractValidSourcesFromAssets(assets, 'Default', 12),
-			).toEqual(expected);
+				expected,
+			);
 		});
 
-		it('should prefer MP4 sources with Loop video style', () => {
+		void it('should prefer MP4 sources with Loop video style', () => {
 			const assets = [mp4Asset480w, m3u8Asset720h, mp4Asset720h];
 			const expected = [mp4Src480w, mp4Src720h, m3u8Src720h];
 
-			expect(extractValidSourcesFromAssets(assets, 'Loop')).toEqual(
+			assert.deepEqual(
+				extractValidSourcesFromAssets(assets, 'Loop'),
 				expected,
 			);
 		});
 
-		it('should prefer MP4 sources with Cinemagraph video style', () => {
+		void it('should prefer MP4 sources with Cinemagraph video style', () => {
 			const assets = [mp4Asset480w, m3u8Asset720h, mp4Asset720h];
 			const expected = [mp4Src480w, mp4Src720h, m3u8Src720h];
 
-			expect(
+			assert.deepEqual(
 				extractValidSourcesFromAssets(assets, 'Cinemagraph'),
-			).toEqual(expected);
+				expected,
+			);
 		});
 	});
 
-	describe('convertFEMediaAssetsToVideoAssets', () => {
+	void describe('convertFEMediaAssetsToVideoAssets', () => {
 		const feMediaAsset480w: FEMediaAsset = {
 			id: 'https://guim-example.co.uk/atomID-1_480w.mp4',
 			version: 1,
@@ -182,41 +190,44 @@ describe('video', () => {
 			hasAudio: true,
 		};
 
-		it('should convert FE media assets to video assets', () => {
-			expect(
+		void it('should convert FE media assets to video assets', () => {
+			assert.deepEqual(
 				convertFEMediaAssetsToVideoAssets([
 					feMediaAsset480w,
 					feMediaAsset720h,
 				]),
-			).toEqual([
-				{
-					url: 'https://guim-example.co.uk/atomID-1_480w.mp4',
-					mimeType: 'video/mp4',
-					dimensions: {
-						height: 384,
-						width: 480,
+				[
+					{
+						url: 'https://guim-example.co.uk/atomID-1_480w.mp4',
+						mimeType: 'video/mp4',
+						aspectRatio: undefined,
+						dimensions: {
+							height: 384,
+							width: 480,
+						},
+						hasAudio: true,
 					},
-					hasAudio: true,
-				},
-				{
-					url: 'https://guim-example.co.uk/atomID-1_720h.mp4',
-					mimeType: 'video/mp4',
-					dimensions: {
-						height: 720,
-						width: 900,
+					{
+						url: 'https://guim-example.co.uk/atomID-1_720h.mp4',
+						mimeType: 'video/mp4',
+						aspectRatio: undefined,
+						dimensions: {
+							height: 720,
+							width: 900,
+						},
+						hasAudio: true,
 					},
-					hasAudio: true,
-				},
-			]);
+				],
+			);
 		});
 
-		it('should return an empty array when given an empty array', () => {
-			expect(convertFEMediaAssetsToVideoAssets([])).toEqual([]);
+		void it('should return an empty array when given an empty array', () => {
+			assert.deepEqual(convertFEMediaAssetsToVideoAssets([]), []);
 		});
 	});
 
-	describe('getAspectRatioFromSources', () => {
-		it('should return the aspect ratio from the first source if it is defined', () => {
+	void describe('getAspectRatioFromSources', () => {
+		void it('should return the aspect ratio from the first source if it is defined', () => {
 			const testSource: Source = {
 				...mp4Src480w,
 				height: 720,
@@ -227,12 +238,13 @@ describe('video', () => {
 
 			const fiveThreeAspectRatio = 1.667;
 
-			expect(getAspectRatioFromSources([testSource])).toEqual(
+			assert.deepEqual(
+				getAspectRatioFromSources([testSource]),
 				fiveThreeAspectRatio,
 			);
 		});
 
-		it('should calculate the aspect ratio from the width and height if aspect ratio is missing', () => {
+		void it('should calculate the aspect ratio from the width and height if aspect ratio is missing', () => {
 			const testSource: Source = {
 				...mp4Src480w,
 				height: 720,
@@ -243,12 +255,13 @@ describe('video', () => {
 
 			const twoThreeAspectRatio = 0.667;
 
-			expect(getAspectRatioFromSources([testSource])).toEqual(
+			assert.deepEqual(
+				getAspectRatioFromSources([testSource]),
 				twoThreeAspectRatio,
 			);
 		});
 
-		it('should return the default aspect ratio if the aspect ratio is undefined and width is 0', () => {
+		void it('should return the default aspect ratio if the aspect ratio is undefined and width is 0', () => {
 			const testSource: Source = {
 				...mp4Src480w,
 				height: 720,
@@ -256,10 +269,10 @@ describe('video', () => {
 				aspectRatio: undefined,
 				hasAudio: true,
 			};
-			expect(getAspectRatioFromSources([testSource])).toEqual(5 / 4);
+			assert.deepEqual(getAspectRatioFromSources([testSource]), 5 / 4);
 		});
 
-		it('should return the default aspect ratio if the aspect ratio is undefined and height is 0', () => {
+		void it('should return the default aspect ratio if the aspect ratio is undefined and height is 0', () => {
 			const testSource: Source = {
 				...mp4Src480w,
 				height: 0,
@@ -267,11 +280,11 @@ describe('video', () => {
 				aspectRatio: undefined,
 				hasAudio: true,
 			};
-			expect(getAspectRatioFromSources([testSource])).toEqual(5 / 4);
+			assert.deepEqual(getAspectRatioFromSources([testSource]), 5 / 4);
 		});
 	});
 
-	describe('findOptimisedSourcePerMimeType', () => {
+	void describe('findOptimisedSourcePerMimeType', () => {
 		const testSources: Source[] = [
 			mp4Src480w,
 			mp4Src720h,
@@ -279,7 +292,7 @@ describe('video', () => {
 			m3u8Src720h,
 		];
 
-		it('selects the smaller videos when there are multiple and all are larger than the screen width.', () => {
+		void it('selects the smaller videos when there are multiple and all are larger than the screen width.', () => {
 			const screenWidth = 400;
 
 			const sources = findOptimisedSourcePerMimeType(
@@ -287,10 +300,10 @@ describe('video', () => {
 				screenWidth,
 			);
 
-			expect(sources).toEqual([mp4Src480w, m3u8Src480w]);
+			assert.deepEqual(sources, [mp4Src480w, m3u8Src480w]);
 		});
 
-		it('selects the larger videos when there are two and one is larger than the screen width and one is smaller.', () => {
+		void it('selects the larger videos when there are two and one is larger than the screen width and one is smaller.', () => {
 			const screenWidth = 600;
 
 			const sources = findOptimisedSourcePerMimeType(
@@ -298,10 +311,10 @@ describe('video', () => {
 				screenWidth,
 			);
 
-			expect(sources).toEqual([mp4Src720h, m3u8Src720h]);
+			assert.deepEqual(sources, [mp4Src720h, m3u8Src720h]);
 		});
 
-		it('selects the larger videos when there are multiple and all are smaller than the screen width.', () => {
+		void it('selects the larger videos when there are multiple and all are smaller than the screen width.', () => {
 			const screenWidth = 800;
 
 			const sources = findOptimisedSourcePerMimeType(
@@ -309,10 +322,10 @@ describe('video', () => {
 				screenWidth,
 			);
 
-			expect(sources).toEqual([mp4Src720h, m3u8Src720h]);
+			assert.deepEqual(sources, [mp4Src720h, m3u8Src720h]);
 		});
 
-		it('selects the smaller videos when some are equal to the screen width and others are larger.', () => {
+		void it('selects the smaller videos when some are equal to the screen width and others are larger.', () => {
 			const screenWidth = 480;
 
 			const sources = findOptimisedSourcePerMimeType(
@@ -320,10 +333,10 @@ describe('video', () => {
 				screenWidth,
 			);
 
-			expect(sources).toEqual([mp4Src480w, m3u8Src480w]);
+			assert.deepEqual(sources, [mp4Src480w, m3u8Src480w]);
 		});
 
-		it('selects the larger videos when some are equal to the screen width and others are smaller.', () => {
+		void it('selects the larger videos when some are equal to the screen width and others are smaller.', () => {
 			const screenWidth = 720;
 
 			const sources = findOptimisedSourcePerMimeType(
@@ -331,33 +344,34 @@ describe('video', () => {
 				screenWidth,
 			);
 
-			expect(sources).toEqual([mp4Src720h, m3u8Src720h]);
+			assert.deepEqual(sources, [mp4Src720h, m3u8Src720h]);
 		});
 	});
 
-	describe('convertCurrentTimeToProgressPercentage', () => {
-		it.each([
+	void describe('convertCurrentTimeToProgressPercentage', () => {
+		for (const testCase of [
 			{ currentTime: 0, duration: 23, expectedPercentage: 0 },
 			{ currentTime: 24, duration: 32, expectedPercentage: 75 },
 			{ currentTime: 56, duration: 56, expectedPercentage: 100 },
 			{ currentTime: 12, duration: 11, expectedPercentage: 100 },
 			{ currentTime: -5, duration: 10, expectedPercentage: null },
 			{ currentTime: 5, duration: -10, expectedPercentage: null },
-		])(
-			'should return the correct progress percentage based on the current time and duration',
-			({ currentTime, duration, expectedPercentage }) => {
-				expect(
+		]) {
+			void it('should return the correct progress percentage based on the current time and duration', () => {
+				const { currentTime, duration, expectedPercentage } = testCase;
+				assert.deepEqual(
 					convertCurrentTimeToProgressPercentage(
 						currentTime,
 						duration,
 					),
-				).toEqual(expectedPercentage);
-			},
-		);
+					expectedPercentage,
+				);
+			});
+		}
 	});
 
-	describe('convertProgressPercentageToCurrentTime', () => {
-		it.each([
+	void describe('convertProgressPercentageToCurrentTime', () => {
+		for (const testCase of [
 			{ progressPercentage: 0, duration: 23, expectedCurrentTime: 0 },
 			{ progressPercentage: 75, duration: 32, expectedCurrentTime: 24 },
 			{ progressPercentage: 100, duration: 56, expectedCurrentTime: 56 },
@@ -369,21 +383,23 @@ describe('video', () => {
 				duration: 10,
 				expectedCurrentTime: 0,
 			},
-		])(
-			'should return the correct current time based on the progress percentage and duration',
-			({ progressPercentage, duration, expectedCurrentTime }) => {
-				expect(
+		]) {
+			void it('should return the correct current time based on the progress percentage and duration', () => {
+				const { progressPercentage, duration, expectedCurrentTime } =
+					testCase;
+				assert.deepEqual(
 					convertProgressPercentageToCurrentTime(
 						progressPercentage,
 						duration,
 					),
-				).toEqual(expectedCurrentTime);
-			},
-		);
+					expectedCurrentTime,
+				);
+			});
+		}
 	});
 
-	describe('formatTimeForDisplay', () => {
-		it.each([
+	void describe('formatTimeForDisplay', () => {
+		for (const testCase of [
 			{ timeInSeconds: -1.24, expectedFormattedTime: '0:00' },
 			{ timeInSeconds: 0, expectedFormattedTime: '0:00' },
 			{ timeInSeconds: 59, expectedFormattedTime: '0:59' },
@@ -392,28 +408,30 @@ describe('video', () => {
 			{ timeInSeconds: 92.5, expectedFormattedTime: '1:32' },
 			{ timeInSeconds: 1000, expectedFormattedTime: '16:40' },
 			{ timeInSeconds: 10000, expectedFormattedTime: '166:40' },
-		])(
-			'should return the correct formatted time based on the time in seconds',
-			({ timeInSeconds, expectedFormattedTime }) => {
-				expect(formatTimeForDisplay(timeInSeconds)).toEqual(
+		]) {
+			void it('should return the correct formatted time based on the time in seconds', () => {
+				const { timeInSeconds, expectedFormattedTime } = testCase;
+				assert.deepEqual(
+					formatTimeForDisplay(timeInSeconds),
 					expectedFormattedTime,
 				);
-			},
-		);
+			});
+		}
 	});
-	describe('roundAspectRatio', () => {
-		it.each([
+	void describe('roundAspectRatio', () => {
+		for (const testCase of [
 			{ aspectRatio: 0.56938445, expectedRoundedAspectRatio: 0.569 },
 			{ aspectRatio: 1.277777, expectedRoundedAspectRatio: 1.278 },
 			{ aspectRatio: 1.25, expectedRoundedAspectRatio: 1.25 },
 			{ aspectRatio: 0.8, expectedRoundedAspectRatio: 0.8 },
-		])(
-			'should return the correct aspect ratio rounded to 3 decimal places',
-			({ aspectRatio, expectedRoundedAspectRatio }) => {
-				expect(roundAspectRatio(aspectRatio)).toEqual(
+		]) {
+			void it('should return the correct aspect ratio rounded to 3 decimal places', () => {
+				const { aspectRatio, expectedRoundedAspectRatio } = testCase;
+				assert.deepEqual(
+					roundAspectRatio(aspectRatio),
 					expectedRoundedAspectRatio,
 				);
-			},
-		);
+			});
+		}
 	});
 });
diff --git a/dotcom-rendering/src/model/article-sections.test.ts b/dotcom-rendering/src/model/article-sections.node.test.ts
similarity index 87%
rename from dotcom-rendering/src/model/article-sections.test.ts
rename to dotcom-rendering/src/model/article-sections.node.test.ts
index 079cf8feb77..e635459e027 100644
--- a/dotcom-rendering/src/model/article-sections.test.ts
+++ b/dotcom-rendering/src/model/article-sections.node.test.ts
@@ -1,6 +1,8 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import { findBySubsection } from './article-sections';
 
-describe('returns section for each subsection', () => {
+void describe('returns section for each subsection', () => {
 	const testCases = [
 		[[], 'Guardian'],
 		[['books', 'childrens-books-site'], 'Books'],
@@ -89,10 +91,10 @@ describe('returns section for each subsection', () => {
 		[['tv-and-radio'], 'TvRadio'],
 	] as const;
 
-	it('returns correct Section for each test case', () => {
+	void it('returns correct Section for each test case', () => {
 		for (const [subsections, section] of testCases) {
 			for (const subsection of subsections) {
-				expect(findBySubsection(subsection).name).toEqual(section);
+				assert.equal(findBySubsection(subsection).name, section);
 			}
 		}
 	});
diff --git a/dotcom-rendering/src/model/buildLightboxImages.test.ts b/dotcom-rendering/src/model/buildLightboxImages.node.test.ts
similarity index 67%
rename from dotcom-rendering/src/model/buildLightboxImages.test.ts
rename to dotcom-rendering/src/model/buildLightboxImages.node.test.ts
index d114db1c2ea..a263a9bd793 100644
--- a/dotcom-rendering/src/model/buildLightboxImages.test.ts
+++ b/dotcom-rendering/src/model/buildLightboxImages.node.test.ts
@@ -1,3 +1,5 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import { Standard as ExampleArticle } from '../../fixtures/generated/fe-articles/Standard';
 import { images } from '../../fixtures/generated/images';
 import type { Block } from '../types/blocks';
@@ -75,8 +77,8 @@ const buildBlock = (elements: FEElement[]): Block => ({
 	secondaryDateLine: '',
 });
 
-describe('buildLightboxImages', () => {
-	it("includes a product's own image when it is large enough", () => {
+void describe('buildLightboxImages', () => {
+	void it("includes a product's own image when it is large enough", () => {
 		const product: ProductBlockElement = {
 			...baseProduct,
 			image: largeProductImage,
@@ -84,17 +86,26 @@ describe('buildLightboxImages', () => {
 
 		const result = buildLightboxImages(format, [buildBlock([product])], []);
 
-		expect(result).toHaveLength(1);
-		expect(result[0]).toMatchObject({
-			masterUrl: largeProductImage.url,
-			elementId: product.elementId,
-			width: largeProductImage.width,
-			height: largeProductImage.height,
-			position: 1,
-		});
+		assert.equal(result.length, 1);
+		assert.deepEqual(
+			{
+				masterUrl: result[0]?.masterUrl,
+				elementId: result[0]?.elementId,
+				width: result[0]?.width,
+				height: result[0]?.height,
+				position: result[0]?.position,
+			},
+			{
+				masterUrl: largeProductImage.url,
+				elementId: product.elementId,
+				width: largeProductImage.width,
+				height: largeProductImage.height,
+				position: 1,
+			},
+		);
 	});
 
-	it("excludes a product's own image when it is too small", () => {
+	void it("excludes a product's own image when it is too small", () => {
 		const product: ProductBlockElement = {
 			...baseProduct,
 			image: smallProductImage,
@@ -102,20 +113,20 @@ describe('buildLightboxImages', () => {
 
 		const result = buildLightboxImages(format, [buildBlock([product])], []);
 
-		expect(result).toEqual([]);
+		assert.deepEqual(result, []);
 	});
 
-	it('excludes a product with no image', () => {
+	void it('excludes a product with no image', () => {
 		const result = buildLightboxImages(
 			format,
 			[buildBlock([baseProduct])],
 			[],
 		);
 
-		expect(result).toEqual([]);
+		assert.deepEqual(result, []);
 	});
 
-	it("includes images nested inside a product's content", () => {
+	void it("includes images nested inside a product's content", () => {
 		const product: ProductBlockElement = {
 			...baseProduct,
 			content: [largeImage],
@@ -123,11 +134,11 @@ describe('buildLightboxImages', () => {
 
 		const result = buildLightboxImages(format, [buildBlock([product])], []);
 
-		expect(result).toHaveLength(1);
-		expect(result[0]?.elementId).toEqual(largeImage.elementId);
+		assert.equal(result.length, 1);
+		assert.deepEqual(result[0]?.elementId, largeImage.elementId);
 	});
 
-	it('assigns positions in document order across regular and product images', () => {
+	void it('assigns positions in document order across regular and product images', () => {
 		const product: ProductBlockElement = {
 			...baseProduct,
 			elementId: 'product-2',
@@ -137,14 +148,17 @@ describe('buildLightboxImages', () => {
 
 		const result = buildLightboxImages(format, [buildBlock([product])], []);
 
-		expect(result.map((image) => image.elementId)).toEqual([
-			largeImage.elementId,
-			product.elementId,
-		]);
-		expect(result.map((image) => image.position)).toEqual([1, 2]);
+		assert.deepEqual(
+			result.map((image) => image.elementId),
+			[largeImage.elementId, product.elementId],
+		);
+		assert.deepEqual(
+			result.map((image) => image.position),
+			[1, 2],
+		);
 	});
 
-	it("includes a product's own CTAs on its card image", () => {
+	void it("includes a product's own CTAs on its card image", () => {
 		const product: ProductBlockElement = {
 			...baseProduct,
 			image: largeProductImage,
@@ -153,10 +167,10 @@ describe('buildLightboxImages', () => {
 
 		const result = buildLightboxImages(format, [buildBlock([product])], []);
 
-		expect(result[0]?.productCtas).toEqual(productCtas);
+		assert.deepEqual(result[0]?.productCtas, productCtas);
 	});
 
-	it('omits productCtas entirely when a product has none', () => {
+	void it('omits productCtas entirely when a product has none', () => {
 		const product: ProductBlockElement = {
 			...baseProduct,
 			image: largeProductImage,
@@ -165,10 +179,10 @@ describe('buildLightboxImages', () => {
 
 		const result = buildLightboxImages(format, [buildBlock([product])], []);
 
-		expect(result[0]?.productCtas).toBeUndefined();
+		assert.equal(result[0]?.productCtas, undefined);
 	});
 
-	it("includes the owning product's CTAs on an image nested inside its content", () => {
+	void it("includes the owning product's CTAs on an image nested inside its content", () => {
 		const product: ProductBlockElement = {
 			...baseProduct,
 			content: [largeImage],
@@ -177,11 +191,11 @@ describe('buildLightboxImages', () => {
 
 		const result = buildLightboxImages(format, [buildBlock([product])], []);
 
-		expect(result).toHaveLength(1);
-		expect(result[0]?.productCtas).toEqual(productCtas);
+		assert.equal(result.length, 1);
+		assert.deepEqual(result[0]?.productCtas, productCtas);
 	});
 
-	it("uses the innermost product's CTAs for an image nested inside a product nested in another product's content", () => {
+	void it("uses the innermost product's CTAs for an image nested inside a product nested in another product's content", () => {
 		const innerCtas: ProductCta[] = [
 			{
 				url: 'https://example.com/inner',
@@ -217,11 +231,11 @@ describe('buildLightboxImages', () => {
 			[],
 		);
 
-		expect(result).toHaveLength(1);
-		expect(result[0]?.productCtas).toEqual(innerCtas);
+		assert.equal(result.length, 1);
+		assert.deepEqual(result[0]?.productCtas, innerCtas);
 	});
 
-	it("falls back to the product's own caption for a content image with no caption of its own", () => {
+	void it("falls back to the product's own caption for a content image with no caption of its own", () => {
 		const product: ProductBlockElement = {
 			...baseProduct,
 			image: largeProductImage,
@@ -233,13 +247,16 @@ describe('buildLightboxImages', () => {
 		const contentEntry = result.find(
 			(image) => image.elementId === largeImage.elementId,
 		);
-		expect(contentEntry?.caption).toEqual(largeProductImage.caption);
+		assert.deepEqual(contentEntry?.caption, largeProductImage.caption);
 	});
 
-	it("keeps a content image's own caption instead of falling back to the product's", () => {
+	void it("keeps a content image's own caption instead of falling back to the product's", () => {
 		const imageWithOwnCaption = {
 			...largeImage,
-			data: { ...largeImage.data, caption: "The image's own caption" },
+			data: {
+				...largeImage.data,
+				caption: "The image's own caption",
+			},
 		};
 		const product: ProductBlockElement = {
 			...baseProduct,
@@ -252,10 +269,10 @@ describe('buildLightboxImages', () => {
 		const contentEntry = result.find(
 			(image) => image.elementId === largeImage.elementId,
 		);
-		expect(contentEntry?.caption).toEqual("The image's own caption");
+		assert.deepEqual(contentEntry?.caption, "The image's own caption");
 	});
 
-	it("uses the innermost product's caption for an image nested inside a product nested in another product's content", () => {
+	void it("uses the innermost product's caption for an image nested inside a product nested in another product's content", () => {
 		const innerProductImage: ProductImage = {
 			...largeProductImage,
 			caption: 'Inner product caption',
@@ -286,10 +303,10 @@ describe('buildLightboxImages', () => {
 		const contentEntry = result.find(
 			(image) => image.elementId === largeImage.elementId,
 		);
-		expect(contentEntry?.caption).toEqual(innerProductImage.caption);
+		assert.deepEqual(contentEntry?.caption, innerProductImage.caption);
 	});
 
-	it("keeps a product's content image and card image adjacent, rather than grouping all content images before all card images", () => {
+	void it("keeps a product's content image and card image adjacent, rather than grouping all content images before all card images", () => {
 		const secondImage = images[1];
 
 		const productA: ProductBlockElement = {
@@ -316,16 +333,22 @@ describe('buildLightboxImages', () => {
 			[],
 		);
 
-		expect(result.map((image) => image.elementId)).toEqual([
-			largeImage.elementId,
-			productA.elementId,
-			secondImage.elementId,
-			productB.elementId,
-		]);
-		expect(result.map((image) => image.position)).toEqual([1, 2, 3, 4]);
+		assert.deepEqual(
+			result.map((image) => image.elementId),
+			[
+				largeImage.elementId,
+				productA.elementId,
+				secondImage.elementId,
+				productB.elementId,
+			],
+		);
+		assert.deepEqual(
+			result.map((image) => image.position),
+			[1, 2, 3, 4],
+		);
 	});
 
-	it("gives every sub-image of a MultiImageBlockElement the owning product's CTAs", () => {
+	void it("gives every sub-image of a MultiImageBlockElement the owning product's CTAs", () => {
 		const multiImage: MultiImageBlockElement = {
 			_type: 'model.dotcomrendering.pageElements.MultiImageBlockElement',
 			elementId: 'multi-1',
@@ -339,8 +362,9 @@ describe('buildLightboxImages', () => {
 
 		const result = buildLightboxImages(format, [buildBlock([product])], []);
 
-		expect(result).toHaveLength(2);
-		expect(result.every((image) => image.productCtas === productCtas)).toBe(
+		assert.equal(result.length, 2);
+		assert.equal(
+			result.every((image) => image.productCtas === productCtas),
 			true,
 		);
 	});
diff --git a/dotcom-rendering/src/model/enhance-ad-placeholders.test.ts b/dotcom-rendering/src/model/enhance-ad-placeholders.node.test.ts
similarity index 76%
rename from dotcom-rendering/src/model/enhance-ad-placeholders.test.ts
rename to dotcom-rendering/src/model/enhance-ad-placeholders.node.test.ts
index 09dc975a89d..596cc7c3839 100644
--- a/dotcom-rendering/src/model/enhance-ad-placeholders.test.ts
+++ b/dotcom-rendering/src/model/enhance-ad-placeholders.node.test.ts
@@ -1,3 +1,5 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import { ArticleDesign, ArticleDisplay, Pillar } from '../lib/articleFormat';
 import type {
 	AdPlaceholderBlockElement,
@@ -73,8 +75,8 @@ const elementIsAdPlaceholder = (
 	'model.dotcomrendering.pageElements.AdPlaceholderBlockElement';
 
 // Tests
-describe('enhanceAdPlaceholders', () => {
-	describe('for general articles', () => {
+void describe('enhanceAdPlaceholders', () => {
+	void describe('for general articles', () => {
 		const testCases = [
 			{ paragraphs: 0, expectedPositions: [] },
 			{ paragraphs: 1, expectedPositions: [] },
@@ -107,9 +109,8 @@ describe('enhanceAdPlaceholders', () => {
 			},
 		] satisfies Array<{ paragraphs: number; expectedPositions: number[] }>;
 
-		describe.each(testCases)(
-			'for $paragraphs paragraph(s) in an article',
-			({ paragraphs, expectedPositions }) => {
+		for (const { paragraphs, expectedPositions } of testCases) {
+			void describe(`for ${paragraphs} paragraph(s) in an article`, () => {
 				const elements = getTestParagraphElements(paragraphs);
 				const expectedPlaceholders = expectedPositions.length;
 				const input: FEElement[] = elements;
@@ -123,23 +124,24 @@ describe('enhanceAdPlaceholders', () => {
 					elementIsAdPlaceholder(el) ? [idx] : [],
 				);
 
-				it(`should insert ${expectedPlaceholders} ad placeholder(s)`, () => {
-					expect(placeholderIndices.length).toEqual(
+				void it(`should insert ${expectedPlaceholders} ad placeholder(s)`, () => {
+					assert.deepEqual(
+						placeholderIndices.length,
 						expectedPlaceholders,
 					);
 				});
 
 				if (expectedPlaceholders > 0) {
-					it(`should insert ad placeholder(s) in the expected position(s): ${expectedPositions.join(
+					void it(`should insert ad placeholder(s) in the expected position(s): ${expectedPositions.join(
 						',',
 					)}`, () => {
-						expect(placeholderIndices).toEqual(expectedPositions);
+						assert.deepEqual(placeholderIndices, expectedPositions);
 					});
 				}
-			},
-		);
+			});
+		}
 
-		it('should not insert an ad placeholder before an inline image element, but can insert it after the image', () => {
+		void it('should not insert an ad placeholder before an inline image element, but can insert it after the image', () => {
 			const threeParagraphs = getTestParagraphElements(3);
 
 			const elements = [
@@ -157,17 +159,17 @@ describe('enhanceAdPlaceholders', () => {
 			)(input);
 			const outputPlaceholders = output.filter(elementIsAdPlaceholder);
 
-			expect(outputPlaceholders.length).toEqual(1);
+			assert.deepEqual(outputPlaceholders.length, 1);
 
 			const placeholderIndices = output.flatMap((el, idx) =>
 				elementIsAdPlaceholder(el) ? [idx] : [],
 			);
 
 			// Expect one placeholder to be present after the fourth element only
-			expect(placeholderIndices).toEqual([4]);
+			assert.deepEqual(placeholderIndices, [4]);
 		});
 
-		it('should not insert an ad placeholder after a thumbnail image element', () => {
+		void it('should not insert an ad placeholder after a thumbnail image element', () => {
 			const threeParagraphs = getTestParagraphElements(3);
 
 			const elements = [
@@ -185,17 +187,17 @@ describe('enhanceAdPlaceholders', () => {
 			)(input);
 			const outputPlaceholders = output.filter(elementIsAdPlaceholder);
 
-			expect(outputPlaceholders.length).toEqual(1);
+			assert.deepEqual(outputPlaceholders.length, 1);
 
 			const placeholderIndices = output.flatMap((el, idx) =>
 				elementIsAdPlaceholder(el) ? [idx] : [],
 			);
 
 			// Expect one placeholder to be present after the fifth element only
-			expect(placeholderIndices).toEqual([5]);
+			assert.deepEqual(placeholderIndices, [5]);
 		});
 
-		it('should not insert an ad placeholder after an element which is not an image or text', () => {
+		void it('should not insert an ad placeholder after an element which is not an image or text', () => {
 			const threeParagraphs = getTestParagraphElements(3);
 
 			const elements = [
@@ -213,17 +215,17 @@ describe('enhanceAdPlaceholders', () => {
 			)(input);
 			const outputPlaceholders = output.filter(elementIsAdPlaceholder);
 
-			expect(outputPlaceholders.length).toEqual(1);
+			assert.deepEqual(outputPlaceholders.length, 1);
 
 			const placeholderIndices = output.flatMap((el, idx) =>
 				elementIsAdPlaceholder(el) ? [idx] : [],
 			);
 
 			// Expect one placeholder to be present after the fifth element only
-			expect(placeholderIndices).toEqual([5]);
+			assert.deepEqual(placeholderIndices, [5]);
 		});
 
-		it('should not insert ad placeholders if shouldHideAds is true', () => {
+		void it('should not insert ad placeholders if shouldHideAds is true', () => {
 			const input: FEElement[] = getTestParagraphElements(6);
 
 			const output = enhanceAdPlaceholders(
@@ -233,11 +235,11 @@ describe('enhanceAdPlaceholders', () => {
 			)(input);
 			const outputPlaceholders = output.filter(elementIsAdPlaceholder);
 
-			expect(outputPlaceholders.length).toEqual(0);
+			assert.deepEqual(outputPlaceholders.length, 0);
 		});
 	});
 
-	describe('for gallery articles', () => {
+	void describe('for gallery articles', () => {
 		const testCases = [
 			{ images: 0, expectedPositions: [] },
 			{ images: 1, expectedPositions: [] },
@@ -254,9 +256,8 @@ describe('enhanceAdPlaceholders', () => {
 			},
 		] satisfies Array<{ images: number; expectedPositions: number[] }>;
 
-		describe.each(testCases)(
-			'for $images images(s) in a gallery article',
-			({ images, expectedPositions }) => {
+		for (const { images, expectedPositions } of testCases) {
+			void describe(`for ${images} images(s) in a gallery article`, () => {
 				const elements = getTestImageBlockElements(images);
 				const expectedPlaceholders = expectedPositions.length;
 				const input: FEElement[] = elements;
@@ -270,23 +271,24 @@ describe('enhanceAdPlaceholders', () => {
 					elementIsAdPlaceholder(el) ? [idx] : [],
 				);
 
-				it(`should insert ${expectedPlaceholders} ad placeholder(s)`, () => {
-					expect(placeholderIndices.length).toEqual(
+				void it(`should insert ${expectedPlaceholders} ad placeholder(s)`, () => {
+					assert.deepEqual(
+						placeholderIndices.length,
 						expectedPlaceholders,
 					);
 				});
 
 				if (expectedPlaceholders > 0) {
-					it(`should insert ad placeholder(s) in the expected position(s): ${expectedPositions.join(
+					void it(`should insert ad placeholder(s) in the expected position(s): ${expectedPositions.join(
 						',',
 					)}`, () => {
-						expect(placeholderIndices).toEqual(expectedPositions);
+						assert.deepEqual(placeholderIndices, expectedPositions);
 					});
 				}
-			},
-		);
+			});
+		}
 
-		it('should not insert ad placeholders if shouldHideAds is true', () => {
+		void it('should not insert ad placeholders if shouldHideAds is true', () => {
 			const input: FEElement[] = getTestParagraphElements(6);
 
 			const output = enhanceAdPlaceholders(
@@ -296,10 +298,10 @@ describe('enhanceAdPlaceholders', () => {
 			)(input);
 			const outputPlaceholders = output.filter(elementIsAdPlaceholder);
 
-			expect(outputPlaceholders.length).toEqual(0);
+			assert.deepEqual(outputPlaceholders.length, 0);
 		});
 
-		it('should still insert ad placeholders if renderingTarget is web', () => {
+		void it('should still insert ad placeholders if renderingTarget is web', () => {
 			const input: FEElement[] = getTestParagraphElements(6);
 
 			const output = enhanceAdPlaceholders(
@@ -309,7 +311,7 @@ describe('enhanceAdPlaceholders', () => {
 			)(input);
 			const outputPlaceholders = output.filter(elementIsAdPlaceholder);
 
-			expect(outputPlaceholders.length).toBeGreaterThan(0);
+			assert(outputPlaceholders.length > 0);
 		});
 	});
 });
diff --git a/dotcom-rendering/src/model/enhance-dots.test.ts b/dotcom-rendering/src/model/enhance-dots.node.test.ts
similarity index 81%
rename from dotcom-rendering/src/model/enhance-dots.test.ts
rename to dotcom-rendering/src/model/enhance-dots.node.test.ts
index 2f4720e5724..2a98da3019c 100644
--- a/dotcom-rendering/src/model/enhance-dots.test.ts
+++ b/dotcom-rendering/src/model/enhance-dots.node.test.ts
@@ -1,8 +1,10 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import type { FEElement } from '../types/content';
 import { enhanceDots } from './enhance-dots';
 
-describe('Middot Tests', () => {
-	it('Output should not be the same as input as dot has been replaced', () => {
+void describe('Middot Tests', () => {
+	void it('Output should not be the same as input as dot has been replaced', () => {
 		const input: FEElement[] = [
 			{
 				_type: 'model.dotcomrendering.pageElements.TextBlockElement',
@@ -29,10 +31,10 @@ describe('Middot Tests', () => {
 			},
 		];
 
-		expect(enhanceDots(input)).not.toBe(expectedOutput);
+		assert.notEqual(enhanceDots(input), expectedOutput);
 	});
 
-	it('It does not incorrectly replace * with dot spans', () => {
+	void it('It does not incorrectly replace * with dot spans', () => {
 		const input: FEElement[] = [
 			{
 				_type: 'model.dotcomrendering.pageElements.TextBlockElement',
@@ -70,6 +72,6 @@ describe('Middot Tests', () => {
 			},
 		];
 
-		expect(enhanceDots(input)).toEqual(expectedOutput);
+		assert.deepEqual(enhanceDots(input), expectedOutput);
 	});
 });
diff --git a/dotcom-rendering/src/model/enhance-product-summary.test.ts b/dotcom-rendering/src/model/enhance-product-summary.node.test.ts
similarity index 78%
rename from dotcom-rendering/src/model/enhance-product-summary.test.ts
rename to dotcom-rendering/src/model/enhance-product-summary.node.test.ts
index e53cca12ced..e0ac850f68c 100644
--- a/dotcom-rendering/src/model/enhance-product-summary.test.ts
+++ b/dotcom-rendering/src/model/enhance-product-summary.node.test.ts
@@ -1,3 +1,5 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import { enhanceProductSummary } from './enhance-product-summary';
 import {
 	findEnhancedProductSummary,
@@ -5,8 +7,8 @@ import {
 	productSummaryElement,
 } from './enhance-product-summary.test-helpers';
 
-describe('enhanceProductSummary', () => {
-	it('enhances product summary elements with its selected product elements', () => {
+void describe('enhanceProductSummary', () => {
+	void it('enhances product summary elements with its selected product elements', () => {
 		const selectedIds = ['1', '2'];
 		const input = [
 			productElement(
@@ -37,15 +39,16 @@ describe('enhanceProductSummary', () => {
 		const enhancedProductSummaryElement =
 			findEnhancedProductSummary(output);
 
-		expect(enhancedProductSummaryElement?.products).toHaveLength(2);
-		expect(
+		assert.equal(enhancedProductSummaryElement?.products.length, 2);
+		assert.deepEqual(
 			enhancedProductSummaryElement?.products.map(
 				(mapping) => mapping.productBlock.id,
 			),
-		).toEqual(selectedIds);
+			selectedIds,
+		);
 	});
 
-	it('enhances product summary elements with the correct CTA indices', () => {
+	void it('enhances product summary elements with the correct CTA indices', () => {
 		const summaryProducts = [
 			{ productId: '3', ctaIndex: 1 },
 			{ productId: '1', ctaIndex: 0 },
@@ -77,16 +80,18 @@ describe('enhanceProductSummary', () => {
 		const enhancedProductSummaryElement =
 			findEnhancedProductSummary(output);
 
-		expect(enhancedProductSummaryElement?.products).toHaveLength(2);
-		expect(
+		assert.equal(enhancedProductSummaryElement?.products.length, 2);
+		assert.deepEqual(
 			enhancedProductSummaryElement?.products.map(
 				(mapping) => mapping.ctaIndex,
 			),
-		).toEqual([1, 0]);
-		expect(
+			[1, 0],
+		);
+		assert.deepEqual(
 			enhancedProductSummaryElement?.products.map(
 				(mapping) => mapping.productBlock.id,
 			),
-		).toEqual(['3', '1']);
+			['3', '1'],
+		);
 	});
 });
diff --git a/dotcom-rendering/src/model/enhance-videos.test.ts b/dotcom-rendering/src/model/enhance-videos.node.test.ts
similarity index 69%
rename from dotcom-rendering/src/model/enhance-videos.test.ts
rename to dotcom-rendering/src/model/enhance-videos.node.test.ts
index d434f8da4c1..a2213b2d1c8 100644
--- a/dotcom-rendering/src/model/enhance-videos.test.ts
+++ b/dotcom-rendering/src/model/enhance-videos.node.test.ts
@@ -1,10 +1,12 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import { ArticleDesign, type ArticleFormat } from '../lib/articleFormat';
 import type { FEElement } from '../types/content';
 import { enhanceGuVideos } from './enhance-videos';
 
-describe('Enhance Videos', () => {
-	describe('for GuVideoElement', () => {
-		it('sets the html of the GuVideoBlockElement', () => {
+void describe('Enhance Videos', () => {
+	void describe('for GuVideoElement', () => {
+		void it('sets the html of the GuVideoBlockElement', () => {
 			const html = '<video></video>';
 
 			const videoElement: FEElement = {
@@ -29,7 +31,8 @@ describe('Enhance Videos', () => {
 				design: ArticleDesign.Video,
 			} as unknown as ArticleFormat;
 
-			expect(enhanceGuVideos(format, html)(inputElements)).toEqual(
+			assert.deepEqual(
+				enhanceGuVideos(format, html)(inputElements),
 				expectedOutput,
 			);
 		});
diff --git a/dotcom-rendering/src/model/enhanceCommercialProperties.test.ts b/dotcom-rendering/src/model/enhanceCommercialProperties.node.test.ts
similarity index 77%
rename from dotcom-rendering/src/model/enhanceCommercialProperties.test.ts
rename to dotcom-rendering/src/model/enhanceCommercialProperties.node.test.ts
index 765f6e412a2..251c37e6da5 100644
--- a/dotcom-rendering/src/model/enhanceCommercialProperties.test.ts
+++ b/dotcom-rendering/src/model/enhanceCommercialProperties.node.test.ts
@@ -1,3 +1,5 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import { Labs } from '../../fixtures/generated/fe-articles/Labs';
 import { Standard } from '../../fixtures/generated/fe-articles/Standard';
 import type { CommercialProperties } from '../types/commercial';
@@ -5,15 +7,16 @@ import { enhanceCommercialProperties } from './enhanceCommercialProperties';
 
 const isNumber = (width: unknown): width is number => typeof width === 'number';
 
-describe('Enhance Branding', () => {
-	it('does not change properties if they have no branding', () => {
+void describe('Enhance Branding', () => {
+	void it('does not change properties if they have no branding', () => {
 		const { commercialProperties } = Standard;
-		expect(enhanceCommercialProperties(commercialProperties)).toEqual(
+		assert.deepEqual(
+			enhanceCommercialProperties(commercialProperties),
 			commercialProperties,
 		);
 	});
 
-	it('should have no widths above 140', () => {
+	void it('should have no widths above 140', () => {
 		const { commercialProperties: partial } = Labs;
 		const commercialProperties: CommercialProperties = {
 			...partial,
@@ -43,7 +46,7 @@ describe('Enhance Branding', () => {
 			.map((p) => p.branding?.logo.dimensions.width)
 			.filter(isNumber);
 
-		expect(Math.max(...dimensionsFail)).toBeGreaterThan(140);
+		assert(Math.max(...dimensionsFail) > 140);
 
 		const dimensionsPass = Object.values(
 			enhanceCommercialProperties(commercialProperties),
@@ -51,6 +54,6 @@ describe('Enhance Branding', () => {
 			.map((p) => p.branding?.logo.dimensions.width)
 			.filter(isNumber);
 
-		expect(Math.max(...dimensionsPass)).toBeLessThanOrEqual(140);
+		assert(Math.max(...dimensionsPass) <= 140);
 	});
 });
diff --git a/dotcom-rendering/src/model/enhanceLists.test.ts b/dotcom-rendering/src/model/enhanceLists.node.test.ts
similarity index 89%
rename from dotcom-rendering/src/model/enhanceLists.test.ts
rename to dotcom-rendering/src/model/enhanceLists.node.test.ts
index e59476b04d3..90842a34d17 100644
--- a/dotcom-rendering/src/model/enhanceLists.test.ts
+++ b/dotcom-rendering/src/model/enhanceLists.node.test.ts
@@ -1,9 +1,11 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import type { FEElement } from '../types/content';
 import type { TagType } from '../types/tag';
 import { enhanceLists } from './enhanceLists';
 
-describe('Enhance lists', () => {
-	it('enhances a multi-byline element correctly', () => {
+void describe('Enhance lists', () => {
+	void it('enhances a multi-byline element correctly', () => {
 		const elementsEnhancer = (elements: FEElement[]): FEElement[] =>
 			elements;
 
@@ -92,7 +94,8 @@ describe('Enhance lists', () => {
 			},
 		];
 
-		expect(enhanceLists(elementsEnhancer, tags)(inputElements)).toEqual(
+		assert.deepEqual(
+			enhanceLists(elementsEnhancer, tags)(inputElements),
 			outputElements,
 		);
 	});
diff --git a/dotcom-rendering/src/model/enhanceTags.test.ts b/dotcom-rendering/src/model/enhanceTags.node.test.ts
similarity index 82%
rename from dotcom-rendering/src/model/enhanceTags.test.ts
rename to dotcom-rendering/src/model/enhanceTags.node.test.ts
index 42d074e323f..54186af09e4 100644
--- a/dotcom-rendering/src/model/enhanceTags.test.ts
+++ b/dotcom-rendering/src/model/enhanceTags.node.test.ts
@@ -1,8 +1,10 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import type { FETagType } from '../types/tag';
 import { enhanceTags } from './enhanceTags';
 
-describe('enhanceTags', () => {
-	it('maps a list of FETagType to TagType', () => {
+void describe('enhanceTags', () => {
+	void it('maps a list of FETagType to TagType', () => {
 		const feTags: FETagType[] = [
 			{
 				properties: {
@@ -20,7 +22,7 @@ describe('enhanceTags', () => {
 
 		const tags = enhanceTags(feTags);
 
-		expect(tags).toEqual([
+		assert.deepEqual(tags, [
 			{
 				id: 'profile/morwennaferrier',
 				type: 'Contributor',
diff --git a/dotcom-rendering/src/model/enhanceTimeline.test.ts b/dotcom-rendering/src/model/enhanceTimeline.node.test.ts
similarity index 83%
rename from dotcom-rendering/src/model/enhanceTimeline.test.ts
rename to dotcom-rendering/src/model/enhanceTimeline.node.test.ts
index 3db1b55acf7..6050e307ccc 100644
--- a/dotcom-rendering/src/model/enhanceTimeline.test.ts
+++ b/dotcom-rendering/src/model/enhanceTimeline.node.test.ts
@@ -1,4 +1,5 @@
 import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import { images } from '../../fixtures/generated/images';
 import type { FEElement } from '../../src/types/content';
 import { enhanceTimeline } from './enhanceTimeline';
@@ -140,8 +141,8 @@ const elementsWithMultipleSections: FEElement[] = [
 	},
 ];
 
-describe('enhanceTimeline', () => {
-	it('keeps a main media with a role that is valid', () => {
+void describe('enhanceTimeline', () => {
+	void it('keeps a main media with a role that is valid', () => {
 		const enhanced = enhanceTimeline(identity)(elementsWithNoSections);
 		assert.equal(
 			enhanced[0]?._type,
@@ -150,10 +151,10 @@ describe('enhanceTimeline', () => {
 
 		const timelineEvent = enhanced[0].events[0];
 		assert.notEqual(timelineEvent, undefined);
-		expect(timelineEvent?.main).toBeDefined();
+		assert.notEqual(timelineEvent?.main, undefined);
 	});
 
-	it('drops a main media with a role that is not valid', () => {
+	void it('drops a main media with a role that is not valid', () => {
 		const enhanced = enhanceTimeline(identity)(elementsWithNoSections);
 		assert.equal(
 			enhanced[0]?._type,
@@ -162,10 +163,10 @@ describe('enhanceTimeline', () => {
 
 		const timelineEvent = enhanced[0].events[1];
 		assert.notEqual(timelineEvent, undefined);
-		expect(timelineEvent?.main).toBeUndefined();
+		assert.equal(timelineEvent?.main, undefined);
 	});
 
-	it('keeps a main media without a role', () => {
+	void it('keeps a main media without a role', () => {
 		const enhanced = enhanceTimeline(identity)(elementsWithNoSections);
 		assert.equal(
 			enhanced[0]?._type,
@@ -174,9 +175,9 @@ describe('enhanceTimeline', () => {
 
 		const timelineEvent = enhanced[0].events[2];
 		assert.notEqual(timelineEvent, undefined);
-		expect(timelineEvent?.main).toBeDefined();
+		assert.notEqual(timelineEvent?.main, undefined);
 	});
-	it('keeps a body element with a role that is valid', () => {
+	void it('keeps a body element with a role that is valid', () => {
 		const enhanced = enhanceTimeline(identity)(elementsWithNoSections);
 		assert.equal(
 			enhanced[0]?._type,
@@ -185,10 +186,10 @@ describe('enhanceTimeline', () => {
 
 		const timelineEvent = enhanced[0].events[3];
 		assert.notEqual(timelineEvent, undefined);
-		expect(timelineEvent?.body).toEqual([images[1]]);
+		assert.deepEqual(timelineEvent?.body, [images[1]]);
 	});
 
-	it('drops a body element with a role that is not valid', () => {
+	void it('drops a body element with a role that is not valid', () => {
 		const enhanced = enhanceTimeline(identity)(elementsWithNoSections);
 		assert.equal(
 			enhanced[0]?._type,
@@ -197,10 +198,10 @@ describe('enhanceTimeline', () => {
 
 		const timelineEvent = enhanced[0].events[4];
 		assert.notEqual(timelineEvent, undefined);
-		expect(timelineEvent?.body).toEqual([]);
+		assert.deepEqual(timelineEvent?.body, []);
 	});
 
-	it('keeps a body element without a role', () => {
+	void it('keeps a body element without a role', () => {
 		const enhanced = enhanceTimeline(identity)(elementsWithNoSections);
 		assert.equal(
 			enhanced[0]?._type,
@@ -209,7 +210,7 @@ describe('enhanceTimeline', () => {
 
 		const timelineEvent = enhanced[0].events[5];
 		assert.notEqual(timelineEvent, undefined);
-		expect(timelineEvent?.body).toEqual([
+		assert.deepEqual(timelineEvent?.body, [
 			{
 				_type: 'model.dotcomrendering.pageElements.MediaAtomBlockElement',
 				elementId: 'mock-id',
@@ -219,7 +220,7 @@ describe('enhanceTimeline', () => {
 		]);
 	});
 
-	it('enhances a timeline with one section appropriately', () => {
+	void it('enhances a timeline with one section appropriately', () => {
 		const enhanced = enhanceTimeline(identity)(elementsWithOneSection);
 		assert.equal(
 			enhanced[0]?._type,
@@ -228,10 +229,10 @@ describe('enhanceTimeline', () => {
 
 		const timelineSection = enhanced[0].sections[0];
 		assert.notEqual(timelineSection, undefined);
-		expect(timelineSection?.title).toEqual('Section 1');
+		assert.deepEqual(timelineSection?.title, 'Section 1');
 	});
 
-	it('enhances a timeline with multiple sections appropriately', () => {
+	void it('enhances a timeline with multiple sections appropriately', () => {
 		const enhanced = enhanceTimeline(identity)(
 			elementsWithMultipleSections,
 		);
@@ -241,6 +242,6 @@ describe('enhanceTimeline', () => {
 		);
 
 		const timelineSections = enhanced[0].sections;
-		expect(timelineSections).toHaveLength(2);
+		assert.equal(timelineSections.length, 2);
 	});
 });
diff --git a/dotcom-rendering/src/model/extractTrendingTopics.test.ts b/dotcom-rendering/src/model/extractTrendingTopics.node.test.ts
similarity index 81%
rename from dotcom-rendering/src/model/extractTrendingTopics.test.ts
rename to dotcom-rendering/src/model/extractTrendingTopics.node.test.ts
index 1dca8ddceb0..344beb78336 100644
--- a/dotcom-rendering/src/model/extractTrendingTopics.test.ts
+++ b/dotcom-rendering/src/model/extractTrendingTopics.node.test.ts
@@ -1,3 +1,5 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import type { FETagType } from '../types/tag';
 import type {
 	NarrowedFECollectionType,
@@ -43,8 +45,8 @@ const tagD = tag('d');
 const tagE = tag('e');
 const tagF = tag('f');
 
-describe('extractTrendingTopics', () => {
-	it('returns tags in correct order with normal input', () => {
+void describe('extractTrendingTopics', () => {
+	void it('returns tags in correct order with normal input', () => {
 		const collection: NarrowedFECollectionType = {
 			curated: [
 				card('a', [tagA]),
@@ -58,12 +60,13 @@ describe('extractTrendingTopics', () => {
 			],
 		};
 
-		expect(
+		assert.deepEqual(
 			extractTrendingTopicsFomFront([collection], 'au/environment'),
-		).toEqual([tagA, tagB, tagC, tagD, tagE, tagF]);
+			[tagA, tagB, tagC, tagD, tagE, tagF],
+		);
 	});
 
-	it('deduplicates cards', () => {
+	void it('deduplicates cards', () => {
 		const collection: NarrowedFECollectionType = {
 			curated: [
 				card('a', [tagA]),
@@ -82,15 +85,16 @@ describe('extractTrendingTopics', () => {
 			curated: [card('g', [tagF])],
 			backfill: [card('g', [tagF])],
 		};
-		expect(
+		assert.deepEqual(
 			extractTrendingTopicsFomFront(
 				[collection, secondCollection],
 				'au/environment',
 			),
-		).toEqual([tagA, tagB, tagC, tagD, tagE, tagF]);
+			[tagA, tagB, tagC, tagD, tagE, tagF],
+		);
 	});
 
-	it('removes cards with id matching pageId', () => {
+	void it('removes cards with id matching pageId', () => {
 		const tagWithPageId = tag('au/environment');
 		const collection: NarrowedFECollectionType = {
 			curated: [
@@ -104,12 +108,13 @@ describe('extractTrendingTopics', () => {
 				card('f', [tagWithPageId, tagA, tagB, tagC, tagD, tagE, tagF]),
 			],
 		};
-		expect(
+		assert.deepEqual(
 			extractTrendingTopicsFomFront([collection], 'au/environment'),
-		).toEqual([tagA, tagB, tagC, tagD, tagE, tagF]);
+			[tagA, tagB, tagC, tagD, tagE, tagF],
+		);
 	});
 
-	it('removes cards without paidContentType or tagType being Keyword or Topics', () => {
+	void it('removes cards without paidContentType or tagType being Keyword or Topics', () => {
 		const tagWithTopicsPaidContentType = tag(
 			'tagWithTopicsPaidContentType',
 			'',
@@ -148,12 +153,13 @@ describe('extractTrendingTopics', () => {
 				]),
 			],
 		};
-		expect(
+		assert.deepEqual(
 			extractTrendingTopicsFomFront([collection], 'au/environment'),
-		).toEqual([
-			tagWithTopicsPaidContentType,
-			tagWithKeywordPaidContentType,
-			tagWithKeywordTagType,
-		]);
+			[
+				tagWithTopicsPaidContentType,
+				tagWithKeywordPaidContentType,
+				tagWithKeywordTagType,
+			],
+		);
 	});
 });
diff --git a/dotcom-rendering/src/model/groupTrailsByDates.test.ts b/dotcom-rendering/src/model/groupTrailsByDates.node.test.ts
similarity index 64%
rename from dotcom-rendering/src/model/groupTrailsByDates.test.ts
rename to dotcom-rendering/src/model/groupTrailsByDates.node.test.ts
index b31cf6efe71..0f72fc1b7ef 100644
--- a/dotcom-rendering/src/model/groupTrailsByDates.test.ts
+++ b/dotcom-rendering/src/model/groupTrailsByDates.node.test.ts
@@ -1,3 +1,5 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import { trails } from '../../fixtures/manual/trails';
 import type { DCRFrontCard } from '../types/front';
 import { groupTrailsByDates } from './groupTrailsByDates';
@@ -9,8 +11,8 @@ const datesToTrails = (dates: Date[]): DCRFrontCard[] => {
 	}));
 };
 
-describe('groupTrailsByDates', () => {
-	it('Will split trails into days & months depending on the frequency', () => {
+void describe('groupTrailsByDates', () => {
+	void it('Will split trails into days & months depending on the frequency', () => {
 		const dates = [
 			// SHOULD BE GROUPED BY DAY
 			// 3 on the 23rd of June
@@ -45,15 +47,15 @@ describe('groupTrailsByDates', () => {
 
 		const result = groupTrailsByDates(datesToTrails(dates), 'UK');
 
-		expect(result[0]?.day).toEqual('26');
-		expect(result[1]?.day).toEqual('25');
-		expect(result[2]?.day).toEqual('23');
+		assert.deepEqual(result[0]?.day, '26');
+		assert.deepEqual(result[1]?.day, '25');
+		assert.deepEqual(result[2]?.day, '23');
 
-		expect(result[3]?.day).toEqual(undefined);
-		expect(result[3]?.month).toEqual('May');
+		assert.deepEqual(result[3]?.day, undefined);
+		assert.deepEqual(result[3]?.month, 'May');
 	});
 
-	it('Will handle all editions', () => {
+	void it('Will handle all editions', () => {
 		const dates = [
 			// The whole of the last day of June (months are 0-indexed)
 			'2024-06-30T00:00:00Z',
@@ -84,33 +86,33 @@ describe('groupTrailsByDates', () => {
 
 		const uk = groupTrailsByDates(datesToTrails(dates), 'UK');
 
-		expect(uk[1]?.day).toEqual('30');
-		expect(uk[1]?.month).toEqual('June');
-		expect(uk[1]?.trails).toHaveLength(23);
-		expect(uk[0]?.day).toBeUndefined();
-		expect(uk[0]?.month).toEqual('July');
-		expect(uk[0]?.trails).toHaveLength(1);
+		assert.deepEqual(uk[1]?.day, '30');
+		assert.deepEqual(uk[1]?.month, 'June');
+		assert.equal(uk[1]?.trails.length, 23);
+		assert.equal(uk[0]?.day, undefined);
+		assert.deepEqual(uk[0]?.month, 'July');
+		assert.equal(uk[0]?.trails.length, 1);
 
 		const au = groupTrailsByDates(datesToTrails(dates), 'AU');
 
-		expect(au[1]?.day).toEqual('30');
-		expect(au[1]?.month).toEqual('June');
-		expect(au[1]?.trails).toHaveLength(14);
-		expect(au[0]?.day).toEqual('1');
-		expect(au[0]?.month).toEqual('July');
-		expect(au[0]?.trails).toHaveLength(10);
+		assert.deepEqual(au[1]?.day, '30');
+		assert.deepEqual(au[1]?.month, 'June');
+		assert.equal(au[1]?.trails.length, 14);
+		assert.deepEqual(au[0]?.day, '1');
+		assert.deepEqual(au[0]?.month, 'July');
+		assert.equal(au[0]?.trails.length, 10);
 
 		const us = groupTrailsByDates(datesToTrails(dates), 'US');
 
-		expect(us[1]?.day).toEqual('29');
-		expect(us[1]?.month).toEqual('June');
-		expect(us[1]?.trails).toHaveLength(4);
-		expect(us[0]?.day).toEqual('30');
-		expect(us[0]?.month).toEqual('June');
-		expect(us[0]?.trails).toHaveLength(20);
+		assert.deepEqual(us[1]?.day, '29');
+		assert.deepEqual(us[1]?.month, 'June');
+		assert.equal(us[1]?.trails.length, 4);
+		assert.deepEqual(us[0]?.day, '30');
+		assert.deepEqual(us[0]?.month, 'June');
+		assert.equal(us[0]?.trails.length, 20);
 	});
 
-	it('Will respect "forceDay" being set to true', () => {
+	void it('Will respect "forceDay" being set to true', () => {
 		const dates = [
 			// This would be grouped by month if left to the pop out frequency
 			// 1 on the 2nd of May
@@ -126,9 +128,9 @@ describe('groupTrailsByDates', () => {
 
 		const result = groupTrailsByDates(datesToTrails(dates), 'UK', true);
 
-		expect(result[0]?.day).toEqual('5');
-		expect(result[1]?.day).toEqual('4');
-		expect(result[2]?.day).toEqual('3');
-		expect(result[3]?.day).toEqual('2');
+		assert.deepEqual(result[0]?.day, '5');
+		assert.deepEqual(result[1]?.day, '4');
+		assert.deepEqual(result[2]?.day, '3');
+		assert.deepEqual(result[3]?.day, '2');
 	});
 });
diff --git a/dotcom-rendering/src/model/unwrapHtml.test.ts b/dotcom-rendering/src/model/unwrapHtml.node.test.ts
similarity index 70%
rename from dotcom-rendering/src/model/unwrapHtml.test.ts
rename to dotcom-rendering/src/model/unwrapHtml.node.test.ts
index 6ff786cb5f6..72a54fe0567 100644
--- a/dotcom-rendering/src/model/unwrapHtml.test.ts
+++ b/dotcom-rendering/src/model/unwrapHtml.node.test.ts
@@ -1,9 +1,11 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import { unwrapHtml } from './unwrapHtml';
 
 type Params = Parameters<typeof unwrapHtml>[0];
 
-describe('unwrapHtml', () => {
-	it('Returns unwrapped HTML if prefix and suffix match', () => {
+void describe('unwrapHtml', () => {
+	void it('Returns unwrapped HTML if prefix and suffix match', () => {
 		// Blockquote, elements inside
 		const bqUnwrap: Params = {
 			html: '<blockquote class="quote"><p>inner</p></blockquote>',
@@ -32,13 +34,13 @@ describe('unwrapHtml', () => {
 			unwrapHtml(pUnwrap);
 
 		// Testy test
-		expect(bqIsUnwrapped).toBeTruthy();
-		expect(bqUnwrappedHtml).toBe('<p>inner</p>');
-		expect(pIsUnwrapped).toBeTruthy();
-		expect(pUnwrappedHtml).toBe('inner');
+		assert(bqIsUnwrapped);
+		assert.equal(bqUnwrappedHtml, '<p>inner</p>');
+		assert(pIsUnwrapped);
+		assert.equal(pUnwrappedHtml, 'inner');
 	});
 
-	it('Returns non-unwrapped HTML if prefix and suffix do not match', () => {
+	void it('Returns non-unwrapped HTML if prefix and suffix do not match', () => {
 		const bqUnwrap: Params = {
 			html: '<blockquote><p>inner</p></blockquote>',
 			fixes: [
@@ -50,11 +52,11 @@ describe('unwrapHtml', () => {
 		};
 		const { willUnwrap: isUnwrapped, unwrappedHtml } = unwrapHtml(bqUnwrap);
 
-		expect(isUnwrapped).toBeFalsy();
-		expect(unwrappedHtml).toBe(bqUnwrap.html);
+		assert(!isUnwrapped);
+		assert.equal(unwrappedHtml, bqUnwrap.html);
 	});
 
-	it('Returns wrapped HTML if prefix and suffix of one "fix" match from multiple options', () => {
+	void it('Returns wrapped HTML if prefix and suffix of one "fix" match from multiple options', () => {
 		const bqUnwrap: Params = {
 			html: '<blockquote><p>inner</p></blockquote>',
 			fixes: [
@@ -121,16 +123,16 @@ describe('unwrapHtml', () => {
 			unwrappedElement: ulUnwrappedElement,
 		} = unwrapHtml(ulUnwrap);
 
-		expect(bqIsUnwrapped).toBeTruthy();
-		expect(bqUnwrappedHtml).toBe('<p>inner</p>');
-		expect(bqUnwrappedElement).toBe('blockquote');
+		assert(bqIsUnwrapped);
+		assert.equal(bqUnwrappedHtml, '<p>inner</p>');
+		assert.equal(bqUnwrappedElement, 'blockquote');
 
-		expect(pIsUnwrapped).toBeTruthy();
-		expect(pUnwrappedHtml).toBe('inner');
-		expect(pUnwrappedElement).toBe('p');
+		assert(pIsUnwrapped);
+		assert.equal(pUnwrappedHtml, 'inner');
+		assert.equal(pUnwrappedElement, 'p');
 
-		expect(ulIsUnwrapped).toBeTruthy();
-		expect(ulUnwrappedHtml).toBe('<li>Test</li><li>test2</li>');
-		expect(ulUnwrappedElement).toBe('ul');
+		assert(ulIsUnwrapped);
+		assert.equal(ulUnwrappedHtml, '<li>Test</li><li>test2</li>');
+		assert.equal(ulUnwrappedElement, 'ul');
 	});
 });
diff --git a/dotcom-rendering/src/model/validate.test.ts b/dotcom-rendering/src/model/validate.node.test.ts
similarity index 72%
rename from dotcom-rendering/src/model/validate.test.ts
rename to dotcom-rendering/src/model/validate.node.test.ts
index 5a969f89503..f189a04d640 100644
--- a/dotcom-rendering/src/model/validate.test.ts
+++ b/dotcom-rendering/src/model/validate.node.test.ts
@@ -1,7 +1,5 @@
-/**
- * @jest-environment node
- */
-
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import { Comment } from '../../fixtures/generated/fe-articles/Comment';
 import { Feature } from '../../fixtures/generated/fe-articles/Feature';
 import { Live } from '../../fixtures/generated/fe-articles/Live';
@@ -55,21 +53,21 @@ const hostedContentArticles = [
 	},
 ];
 
-describe('validate', () => {
-	it('throws on invalid data', () => {
+void describe('validate', () => {
+	void it('throws on invalid data', () => {
 		const data = { foo: 'bar' };
-		expect(() => validateAsFEArticle(data)).toThrow(TypeError);
+		assert.throws(() => validateAsFEArticle(data), TypeError);
 	});
 
 	for (const article of articles) {
-		it(`validates data for a ${article.name} article`, () => {
-			expect(validateAsFEArticle(article.data)).toBe(article.data);
+		void it(`validates data for a ${article.name} article`, () => {
+			assert.equal(validateAsFEArticle(article.data), article.data);
 		});
 	}
 
 	for (const hostedItem of hostedContentArticles) {
-		it(`validates data for hosted ${hostedItem.name} content`, () => {
-			expect(validateAsFEArticle(hostedItem.data)).toBe(hostedItem.data);
+		void it(`validates data for hosted ${hostedItem.name} content`, () => {
+			assert.equal(validateAsFEArticle(hostedItem.data), hostedItem.data);
 		});
 	}
 });
diff --git a/dotcom-rendering/src/model/validate.puzzlesPage.test.ts b/dotcom-rendering/src/model/validate.puzzlesPage.node.test.ts
similarity index 73%
rename from dotcom-rendering/src/model/validate.puzzlesPage.test.ts
rename to dotcom-rendering/src/model/validate.puzzlesPage.node.test.ts
index d28f902092b..1029111ed50 100644
--- a/dotcom-rendering/src/model/validate.puzzlesPage.test.ts
+++ b/dotcom-rendering/src/model/validate.puzzlesPage.node.test.ts
@@ -1,3 +1,5 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
 import { validateAsPuzzlesPageType } from './validate';
 
 const validPage = () => ({
@@ -37,25 +39,26 @@ const validPage = () => ({
 	},
 });
 
-describe('validateAsPuzzlesPageType', () => {
-	it('accepts a valid recursive blueprint contract', () => {
-		expect(
+void describe('validateAsPuzzlesPageType', () => {
+	void it('accepts a valid recursive blueprint contract', () => {
+		assert.equal(
 			validateAsPuzzlesPageType(validPage()).layout.containers[0]?.id,
-		).toBe('word-games');
+			'word-games',
+		);
 	});
 
-	it('accepts enabled on featured containers and rejects it elsewhere', () => {
+	void it('accepts enabled on featured containers and rejects it elsewhere', () => {
 		const featuredPage = validPage();
 		featuredPage.layout.containers[0]!.variant = 'featured';
 		(featuredPage.layout.containers[0] as { enabled?: boolean }).enabled =
 			true;
-		expect(validateAsPuzzlesPageType(featuredPage)).toBeDefined();
+		assert.notEqual(validateAsPuzzlesPageType(featuredPage), undefined);
 
 		featuredPage.layout.containers[0]!.variant = 'standard';
-		expect(() => validateAsPuzzlesPageType(featuredPage)).toThrow();
+		assert.throws(() => validateAsPuzzlesPageType(featuredPage));
 	});
 
-	it.each([
+	for (const [name, mutate] of [
 		[
 			'unknown card variant',
 			(page: ReturnType<typeof validPage>) => {
@@ -100,15 +103,17 @@ describe('validateAsPuzzlesPageType', () => {
 				});
 			},
 		],
-	])('rejects %s', (_, mutate) => {
-		const page = validPage();
-		mutate(page);
-		expect(() => validateAsPuzzlesPageType(page)).toThrow(
-			'Unable to validate request body for puzzles page',
-		);
-	});
+	] as const) {
+		void it(`rejects ${name}`, () => {
+			const page = validPage();
+			mutate(page);
+			assert.throws(() => validateAsPuzzlesPageType(page), {
+				message: 'Unable to validate request body for puzzles page.',
+			});
+		});
+	}
 
-	it('accepts supporting content with valid puzzle references', () => {
+	void it('accepts supporting content with valid puzzle references', () => {
 		const page = validPage();
 		page.layout.containers.push({
 			id: 'supporting',
@@ -131,12 +136,13 @@ describe('validateAsPuzzlesPageType', () => {
 			},
 		} as never);
 
-		expect(validateAsPuzzlesPageType(page).layout.containers).toHaveLength(
+		assert.equal(
+			validateAsPuzzlesPageType(page).layout.containers.length,
 			2,
 		);
 	});
 
-	it('rejects supporting content which references an unknown puzzle', () => {
+	void it('rejects supporting content which references an unknown puzzle', () => {
 		const page = validPage();
 		page.layout.containers.push({
 			id: 'supporting',
@@ -151,10 +157,10 @@ describe('validateAsPuzzlesPageType', () => {
 			},
 		} as never);
 
-		expect(() => validateAsPuzzlesPageType(page)).toThrow();
+		assert.throws(() => validateAsPuzzlesPageType(page));
 	});
 
-	it('accepts a valid top-level ad placement and rejects one nested inside content', () => {
+	void it('accepts a valid top-level ad placement and rejects one nested inside content', () => {
 		const page = validPage();
 		const ad = {
 			id: 'inline-ad',
@@ -164,11 +170,12 @@ describe('validateAsPuzzlesPageType', () => {
 			content: { items: [], nestedContainers: [] },
 		};
 		page.layout.containers.push(ad as never);
-		expect(validateAsPuzzlesPageType(page).layout.containers).toHaveLength(
+		assert.equal(
+			validateAsPuzzlesPageType(page).layout.containers.length,
 			2,
 		);
 		page.layout.containers.pop();
 		page.layout.containers[0]!.content.nestedContainers.push(ad as never);
-		expect(() => validateAsPuzzlesPageType(page)).toThrow();
+		assert.throws(() => validateAsPuzzlesPageType(page));
 	});
 });