[WIP] Fix CI for PR #148 by adding missing unit tests and e2e tests

[Copilot]

• Install dependencies and verify base TS check passes
• Create src/commands/clean.test.ts (use vi.hoisted for mockReaddir with Dirent<string> typing to avoid overload resolution issue)
• Create src/commands/default-prefs-userjs.test.ts (fix spy type, annotate c: unknown[] in .mock.calls.map)
• Create src/commands/diff.test.ts (fix spy types for log and info, annotate c: unknown[])
• Update src/lib/cli.test.ts (add parseKeepArgument tests, fix spy type, annotate c: unknown[])
• Update src/lib/firefox.test.ts (add comparePrefs tests with explicit Map<string, Pref> typing)
• Create src/lib/format.test.ts (no fixes needed)
• Update src/index.end-to-end.test.ts (add activate command and error handling tests)
• npm run check:typescript passes (0 errors)
• npm test passes (141 tests in 9 files)

Original prompt

Fix CI for PR #148 (Add missing unit tests and e2e tests) in martabal/ff-diff without introducing regressions.

Context:

• PR: Add missing unit tests and e2e tests #148
• Head branch: copilot/suggest-missing-unit-e2e-tests
• Base: main
• CI failing in TypeScript check (tsc --noEmit). Job log excerpt shows errors in new/modified tests:
  • Type '"log"' does not satisfy the constraint '"Console"' (and similarly for "info") in multiple test files: src/commands/clean.test.ts, src/commands/default-prefs-userjs.test.ts, src/commands/diff.test.ts, src/lib/cli.test.ts.
  • Dirent<string> not assignable to Dirent<NonSharedBuffer> in src/commands/clean.test.ts where test helper returns a Dirent.
  • No overload matches this call in src/lib/firefox.test.ts around constructing new Map([...]) due to inferred value type being boolean but includes number too.

Requirements:

1. Update the tests to typecheck under the repo’s TS configuration and Node types.
   • Avoid incorrect ReturnType<typeof vi.spyOn<Console, "log">> generic usage that triggers TS2344.
   • Fix the Dirent typing issues (likely by loosening mock entry typing or using Dirent without generic, or adjust mock so it conforms to Node’s expected Dirent<NonSharedBuffer> typing).
   • Fix comparePrefs tests in src/lib/firefox.test.ts so Map value type is correctly inferred/declared (should match the Pref type used in the library: string | number | boolean).
2. Keep test intent/coverage; do not reduce assertions in a way that could mask real regressions.
3. Ensure npm test (vitest) and npm run check:typescript pass.
4. Do not change production behavior unless required for typing correctness of tests.

Deliverable:

• A PR from the existing head branch updating only necessary test code (and types/imports) so CI passes.

The following is the prior conversation context from the user's chat exploration (may be truncated):

User: fix CI and do not add regressions

Assistant: I’m waiting for you to accept or reject the pending action so I can continue fixing the CI failures in PR #148 without introducing regressions.

This pull request was created from Copilot chat.