Fully test the isolated mutation run state

[stefan-burke]

The next chunk after #1951, continuing the work from #1944: taking one scripts/ file at a time up to a full mutation score, so its tests really would catch a change to it.

scripts/mutation/isolation-state.ts now scores 100% — 224 of 224, with nothing suppressed. It was at 78.3%.

What was untested

Most of the gap was the two lists naming what a mutation snapshot must not copy — folders like node_modules, .git, and the coverage output, plus files like .env and the local database. Not one entry was checked, so any of them could have been deleted without a test noticing. Quietly copying node_modules into every snapshot would roughly double how long each mutation run takes; quietly copying .env would put secrets in a temporary folder. Every entry is now checked one by one.

The rest covers rules nothing had pinned down:

• Which files count as a database, so the write-ahead and shared-memory files go too, not just the .db itself.
• Which built browser assets are left behind, and that an ordinary file sitting in the same folder still comes along.
• That a folder name is only skipped when it is the top folder — someone's own dist folder further down is theirs to keep.
• That a run id ends in eight letters, so two runs starting in the same second cannot land in one folder.
• That the record written to disk stays readable, indented, one field per line, for anyone who opens it.
• That a whole run id wins outright over one that merely starts the same way, so --kill mutation-abc cannot refuse to act because mutation-abc-2 also exists.
• That the lock genuinely keeps a second run out, that it hands the lock back when the work inside fails, and that a run nobody is holding is reported as free.

Four things that were doing nothing

• Two folder-making calls that repeated the line directly above them.
• docs-output listed as a folder name, when the rule below it already skips anything starting with that.
• tickets.db listed as a file name, when the database-file rule already covers it.
• The run lock was its own copy of withFileLock from scripts/lock-file.ts — opening, holding, releasing and closing in the same order. It now calls that helper and only adds the part that is genuinely its own: making the run's folder first, so there is something there to lock.

scripts/mutation/isolation.ts is still at 100% after that lock change.

Next

The remaining scripts/ files with gaps are stripe-mock.ts, stripe-mock/install.ts, specs/run.ts, and mutation.ts.

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📥 Commits

Reviewing files that changed from the base of the PR and between e383011 and b587df7.

📒 Files selected for processing (7)

• scripts/mutation/isolation-state.ts
• test/scripts/mutation/isolation-state/commands.test.ts
• test/scripts/mutation/isolation-state/env.test.ts
• test/scripts/mutation/isolation-state/lock.test.ts
• test/scripts/mutation/isolation-state/paths.test.ts
• test/scripts/mutation/isolation-state/records.test.ts
• test/scripts/mutation/isolation-state/skips.test.ts

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• Create PR with unit tests
• Commit unit tests in branch claude/mutation-check-isolation-state

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• Commit simplified code in branch claude/mutation-check-isolation-state

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