chore: migrate tests from mocha to vitest (PRE-3838) (#281)

* chore: migrate tests from mocha to vitest

Replace mocha 6 with vitest 4.1.11. done callbacks become awaited
promises with the assertions moved after the await; vitest.config.js
unsets PRERENDER_SERVICE_URL so the suite is hermetic, and runs test
files serially because both Express support apps bind the same port.
Travis now runs on Node 20, the minimum Vitest 4 supports.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

* ci: run the test suite on pull requests

Tests only ran inside the publish job on push to master, so a broken
suite was first seen after merge and blocked the release.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

* chore: keep vitest.config.js and .github out of the npm tarball

vitest.config.js requires vitest, a devDependency consumers don't have.
.github already shipped before this PR; the new test workflow would have
joined it.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Author: marceloprerender

.github/workflows/test.yml

@@ -0,0 +1,32 @@
+name: Test
+
+on:
+  pull_request:
+    branches:
+      - master
+
+permissions:
+  contents: read
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v5
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Setup test dependencies
+        run: |
+          cd test/support/express3 && npm install
+          cd ../express4 && npm install
+
+      - name: Run tests
+        run: npm test

.npmignore

@@ -1,2 +1,4 @@
 test
 .travis.yml
+vitest.config.js
+.github

.travis.yml

@@ -1,6 +1,6 @@
 language: node_js
 node_js:
-  - "10"
+  - "20"
 script:
   - cd test/support/express3 && npm install
   - cd ../express4 && npm install