test: make npm failure diagnostics deterministic

[mohanagy]

Resolves #137.

The Windows Node 22 failure was the captured-output formatter test itself: it launched a real npm exec process while Vitest applied its five-second per-test limit. The production command has its own 25-second lifecycle; the test was not a valid latency assertion.

This keeps real package behavior covered by the existing pack, check:pack, tarball-install, CLI, and smoke contracts. It changes only the formatter unit test to use the existing injectable child-process seam, explicitly writing stdout/stderr and closing with status 1.

No production behavior, timeout, coverage, shell setting, package validation, or process containment changed.

Local validation:

• focused regression: passed
• full tests/package-contract.test.ts: 17 passed
• npm run typecheck: passed
• git diff --check: passed

CI must validate the exact head on Linux, macOS, and all Windows Node versions before merge.

Summary by CodeRabbit

• Tests
  • Improved coverage for failed command handling by simulating process failures deterministically.
  • Verified that error messages include captured standard output and error details.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro Plus

Run ID: 9924de9d-5177-485d-b09e-cd5a1a19c5dc

📥 Commits

Reviewing files that changed from the base of the PR and between d65f3f1 and 0d73aef.

📒 Files selected for processing (1)

• tests/package-contract.test.ts

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📝 Walkthrough

Walkthrough

The package contract test replaces a real npm child process with a mocked process that emits deterministic stdout and stderr before closing with exit status 1, then verifies the rejection includes both captured outputs.

Changes

npm failure handling test

Layer / File(s)	Summary
Mocked process validation tests/package-contract.test.ts	The failure test uses TermIgnoringNpmProcess, emits fixed stdout and stderr content, triggers a failed close event, and checks both outputs in the rejection message.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Poem

A rabbit taps, “No shell today,”

Mocked streams hop along the way.
Though npm fails with status one,
Its captured words are safely spun.
Tests now breathe a steadier air.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly matches the change: making the npm failure diagnostics test deterministic.
Description check	✅ Passed	The description explains the change and validation, but the Security impact section and template-style validation checklist are incomplete.
Linked Issues check	✅ Passed	The test isolation fix addresses [#137] by preserving CLI behavior and coverage while removing the flaky real-process dependency.
Out of Scope Changes check	✅ Passed	Only the targeted formatter test changed, with no unrelated production or packaging edits introduced.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/137-windows-package-contract

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[mohanagy]

Maintainer self-review complete. The diff is limited to the existing runNpm formatter contract: it replaces a real npm exec child with the existing injected child-process seam, emits the same stdout/stderr and non-zero close result, and leaves production execution, timeout policy, package validation, shell settings, and containment unchanged. I found no unresolved human review comments. Current exact-head CI is green across Linux, macOS, and Windows Node 20/22/24; CodeRabbit is still quota-blocked and remains a required gate before merge.

[mohanagy]

@coderabbitai review

[coderabbitai]

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