Harden

Target: $ARGUMENTS (file, directory, or module — if blank, use unstaged changes)

Pre-loaded context

• Test runner: !node -e "const p=require('./package.json'); console.log(p.scripts?.test || 'none')"
• Unstaged changes: !git diff --name-only

Workflow

1. Scope

Identify target files. If $ARGUMENTS is blank, use unstaged changed files.

• Read each target file
• Read its existing test file (co-located *.test.ts or __tests__/)
• If no test file exists, note it

2. Audit

For each file, list findings in three buckets:

Bucket	What to look for
Split	Functions > 20 lines, multiple responsibilities, deeply nested logic (> 2 levels), God functions doing I/O + logic
Edge cases	Missing null/empty/boundary checks at system boundaries, unhandled error paths, implicit assumptions
Test gaps	Untested public functions, branches with no coverage, missing sad-path tests

Present the audit as a checklist. Ask via AskUserQuestion (multiSelect): "Which items should I address?" — list each finding as an option, with "All items" as first option marked (Recommended).

3. Harden (TDD loop per item)

For each approved item, apply red-green-refactor:

RED:    Write a failing test that exposes the gap
GREEN:  Minimal code change to pass
REFACTOR: Extract/simplify if the fix introduced complexity

One item at a time. Run tests after each cycle. Never batch.

Splitting rules:

• Extract pure logic into named helpers — keep I/O at the edges
• New functions must be testable through public interface when possible
• Preserve the original function's signature (no breaking changes)

Test rules:

• Test behavior, not implementation
• Each test gets a descriptive name: it('returns empty array when input is null')
• Prefer real values over mocks; mock only external I/O

4. Verify

• Run full test suite
• Confirm no regressions
• Report summary: items addressed, tests added, functions extracted

Output format

## Hardening Report

### Audit
- [ ] Split: `processOrder` (45 lines, validation + persistence + notification)
- [ ] Edge: `parseConfig` — no handling for missing file
- [ ] Test: `formatOutput` — zero test coverage

### Changes
- Extracted `validateOrder()` from `processOrder()` (+1 fn, +3 tests)
- Added null-guard to `parseConfig` (+2 tests)
- Backfilled `formatOutput` tests (+4 tests)

### Result
Tests: 42 passed (was 35) | 0 failed

Rules

• Never change external behavior — hardening is internal improvement
• If splitting a function would require changing its public API, flag it and ask before proceeding
• Always run tests between items — stop if anything breaks
• Skip files with zero test infrastructure unless user explicitly asks to set it up

Error Handling

• If no test runner found → ask user which runner to use before proceeding
• If test suite fails before hardening → report failures and stop; don't harden broken code
• If a split introduces a regression → revert that split immediately, note it as blocked
• If target file has no exports (script/entrypoint) → audit only, skip test backfill unless user confirms