test: enable v8 coverage instrumentation for 程式碼.js (#107)

[cheerc]

Summary

Refactor backend test files from new Function() sandbox eval to direct require() so v8 coverage provider can instrument 程式碼.js execution.

Problem

程式碼.js showed 0% coverage despite having comprehensive tests in backend.test.js (170+ test cases). The reason: tests used new Function() to wrap the source in a sandbox IIFE, which v8 cannot instrument.

Solution (方案 B)

1. 程式碼.js: Added conditional module.exports at the end — typeof module guard ensures GAS runtime is unaffected (GAS has no module global)
2. Test files: Replaced new Function() sandbox with vi.stubGlobal() + createRequire() + module cache invalidation — each createGasEnv() call still gets a fresh evaluation matching the old sandbox behavior
3. wiringContracts.test.js: Updated to verify exports via direct require() instead of parsing factory return block

Files Changed

File	Change
程式碼.js	Conditional module.exports + _resetSs test helper
tests/unit/backend.test.js	new Function() → require() + vi.stubGlobal()
tests/unit/backendSignatureContracts.test.js	Same refactor
tests/unit/businessLogicEdgeCases.test.js	Same refactor
tests/unit/wiringContracts.test.js	Direct require() verification

Results

Metric	Before	After
Lines	0%	95.04%
Functions	0%	88%
Branches	0%	77.2%
Statements	0%	96.77%

All 1142 existing tests pass. No behavioral changes. ESLint 0 errors.

refs #107
follows spec

[cheerc]

✅ VERIFIED

Reviewed HEAD: a741986
Reviewer: cb-team-reviewer
Audit mode: standard (D2, lenses: correctness + security)

Files Reviewed (5)

• 程式碼.js (+16/-1) — conditional module.exports for v8 coverage instrumentation
• tests/unit/backend.test.js (+29/-31) — sandbox→require refactor
• tests/unit/backendSignatureContracts.test.js (+26/-31) — sandbox→require refactor
• tests/unit/businessLogicEdgeCases.test.js (+16/-26) — sandbox→require refactor
• tests/unit/wiringContracts.test.js (+31/-34) — factory return→direct require

Stage 1 — Correctness

• Conditional export: if (typeof module !== 'undefined') — GAS has no module, block is dead code in production ✓
• Export completeness: all 17 production functions exported + _resetSs test helper ✓
• Consistent refactor: all 4 test files use same pattern (createRequire + vi.stubGlobal + cache invalidation) ✓
• Cache invalidation: delete _require.cache[backendPath] before each require() — ensures fresh evaluation per test (matches old sandbox-per-test isolation) ✓
• _resetSs: test-only helper to reset memoized _ss reference — correct for test isolation ✓
• No conflict markers (5 files clean)

Stage 2 — Security (Conditional Export)

• typeof module !== 'undefined' is standard CJS detection — GAS runtime has no module global → no-op in production ✓
• No sensitive data exposed — only function references already available as global declarations in GAS ✓
• _resetSs only accessible in Node.js test environment, not in GAS production ✓
• eslint-disable no-undef scoped to the export block only ✓

Note

⚠️ PR #155 merged after this branched (base ec3fee7 vs #155 base). May need rebase for vitest.config.js threshold changes.

Evidence

• ran: grep "^function " 程式碼.js → 17 functions
• ran: conflict marker scan (5 files) → all 0
• cited: 程式碼.js:608 — if (typeof module !== 'undefined') (conditional export guard)
• cited: 程式碼.js:609-618 — module.exports = { 17 functions + _resetSs }
• cited: backend.test.js:39-45 — vi.stubGlobal pattern
• cited: backend.test.js:48 — delete _require.cache[backendPath] (cache invalidation)