test: execute the probe's missing-export filter, note the fixture pin coupling

The existing tests drove the runner with canned output, so nothing ran
the filter the probe ships, and a green CI run does not either: the
filter only reports, so breaking it makes every load pass. Verified by
mutation, stubbing the filter to an empty list fails the new case.

Also ties FIREBASE_RANGE to the firebase devDependency in a comment.
They match today and nothing enforces it, so a move to firebase 12
would silently leave the probe exercising 11.

Author: tyler-reitz

scripts/entry-load.mjs

@@ -37,6 +37,12 @@ export const DEFAULT_REACT_VERSIONS = ['18', '19'];
 // Held to the major the repo develops against rather than "latest", so the
 // fixture is deterministic and stays inside the declared peer range
 // (^9 || ^10 || ^11 || ^12).
+//
+// Keep this in step with the `firebase` devDependency in package.json. It
+// matches today, and nothing enforces that: when the repo moves to firebase 12
+// this fixture keeps loading the package against 11 and stays green, so the
+// major the probe actually exercises drifts away from the one CI develops
+// against without any signal.
 export const FIREBASE_RANGE = '^11.10.0';
 
 // A load that resolves but exports nothing is still a broken package, and an

test/entry-load.test.mjs

@@ -1,7 +1,8 @@
 import fs from 'node:fs';
 import os from 'node:os';
 import path from 'node:path';
-import { collectFailures, describeResult, loadWithReact, parseProbeOutput } from '../scripts/entry-load.mjs';
+import { execFileSync } from 'node:child_process';
+import { EXPECTED_EXPORTS, collectFailures, describeResult, loadWithReact, parseProbeOutput, probeSource } from '../scripts/entry-load.mjs';
 
 /**
  * These tests pin the failure detection, not the fixture's shape. `publint` and
@@ -119,3 +120,43 @@ describe('loadWithReact', () => {
     expect(collectFailures([{ react: '18', ...result }])).toHaveLength(1);
   });
 });
+
+/**
+ * The tests above drive the runner with canned output, so none of them execute
+ * the missing-export filter the probe actually ships. A green CI run does not
+ * either: the filter only reports, so breaking it makes every load pass. These
+ * run the generated source against a stand-in module instead of a mock.
+ */
+describe('probeSource', () => {
+  let dir;
+
+  beforeEach(() => {
+    dir = fs.mkdtempSync(path.join(os.tmpdir(), 'reactfire-probe-'));
+  });
+
+  afterEach(() => {
+    fs.rmSync(dir, { recursive: true, force: true });
+  });
+
+  // The probe resolves its target by specifier, so a relative path stands in
+  // for the installed package without needing a fixture install.
+  function runProbe(exports) {
+    fs.writeFileSync(path.join(dir, 'stand-in.mjs'), `export const ${exports.join(' = 1;\nexport const ')} = 1;\n`);
+    fs.writeFileSync(path.join(dir, 'probe.mjs'), probeSource('esm', { name: './stand-in.mjs' }));
+    return parseProbeOutput(execFileSync(process.execPath, [path.join(dir, 'probe.mjs')], { encoding: 'utf8' }));
+  }
+
+  it('passes when every canary is exported', () => {
+    const result = runProbe(EXPECTED_EXPORTS);
+    expect(result.ok).toBe(true);
+  });
+
+  // One dropped submodule is the case the widened canary list exists for, and
+  // the case a broken filter would wave through.
+  it('names the missing canary when one submodule is dropped', () => {
+    const result = runProbe(EXPECTED_EXPORTS.filter((name) => name !== 'useStorageDownloadURL'));
+    expect(result.ok).toBe(false);
+    expect(result.reason).toBe('missing-exports');
+    expect(result.missing).toEqual(['useStorageDownloadURL']);
+  });
+});