Doublecheck Skill

Verify assertions, logic, and assumptions before finalizing changes. This skill provides a structured second-look workflow.

When to Use

• Before committing a non-trivial change
• After completing a debugging session
• When uncertain about edge cases or correctness
• When refactoring critical path code

Verification Checklist

Logic Verification

1. Re-read the changed code and trace the logic step by step.
2. Confirm all conditional branches produce the correct outcome.
3. Check for off-by-one errors, null/undefined edge cases, and type coercion issues.
4. Verify async code handles all Promise rejection paths.

Convention Compliance

1. Confirm I prefix on interfaces, isI prefix on type guards.
2. Verify public-api.ts exports are correct and complete.
3. Check no test types are exported from public-api.ts.
4. Confirm no files under generated/ were modified.
5. Verify Prettier formatting: double quotes, semicolons, 2-space indent.

Test Verification

1. Run affected tests and confirm they pass.
2. Check that tests are self-contained with injectable configuration.
3. Verify test names describe expected behavior.
4. Confirm test files use *.test.ts suffix and correct directory.

Dependency Check

1. Verify no circular dependencies introduced.
2. Confirm cactus-test-tooling is devDependency only.
3. Check imported modules actually exist and are correctly referenced.

Workflow

1. Gather: Read all changed files
2. Trace: Follow logic paths through the changes
3. Verify: Check each item on the checklist above
4. Report: Summarize findings as PASS/FAIL with details

Output Format

## Doublecheck Report

**Scope**: [files checked]
**Result**: ✅ PASS / ❌ FAIL

### Findings
- [PASS/FAIL] Logic verification: [details]
- [PASS/FAIL] Convention compliance: [details]
- [PASS/FAIL] Test verification: [details]
- [PASS/FAIL] Dependency check: [details]

### Issues Found (if any)
1. [specific issue and location]