review-implementation

<skill_overview> Review completed implementation against the epic spec to catch gaps before claiming completion; the spec is the contract, and implementation must fulfill it completely. </skill_overview>

<rigidity_level> LOW FREEDOM - Follow the 4-step review process exactly. Review with Google Fellow-level scrutiny. Never skip automated checks, quality gates, or code reading. No approval without evidence for every criterion. </rigidity_level>

<evidence_requirements>

Evidence-Based Review (Zero Speculation Principle)

Every claim requires evidence:

Claim Type	Required Evidence
"Code implements X"	File path:line number showing implementation
"Test covers Y"	Test name + specific assertion
"Criterion met"	Command output proving criterion
"No anti-pattern"	Search command showing no matches

Confidence Scores:

Rate each finding 0.0-1.0:

• 1.0 - Verified with direct evidence (ran command, read code)
• 0.8 - Strong indirect evidence (multiple consistent signals)
• 0.5 - Uncertain (partial evidence, assumptions made)
• 0.3 - Weak (limited investigation, needs more verification)

Findings below 0.8 confidence must be investigated until ≥0.8 or marked UNCERTAIN.

Example evidence format:

| Criterion | Status | Confidence | Evidence |
|-----------|--------|------------|----------|
| All tests pass | ✅ Met | 1.0 | `cargo test`: 127 passed, 0 failed |
| No unwrap in production | ❌ Not met | 1.0 | `rg "\.unwrap\(\)" src/`: Found at jwt.ts:45 |
| Error handling proper | ⚠️ Uncertain | 0.5 | Read jwt.ts, unclear if all paths covered |

</evidence_requirements>

<quick_reference>

Step	Action	Deliverable
1	Load bd epic + all tasks	TodoWrite with tasks to review
2	Review each task (automated checks, quality gates, read code, audit tests, verify criteria)	Findings per task
3	Report findings (approved / gaps found)	Review decision
4	Gate: If approved → finishing-a-development-branch, If gaps → STOP	Next action

Review Perspective: Google Fellow-level SRE with 20+ years experience reviewing junior engineer code.

Test Quality Gate: Every new test must catch a real bug. Tautological tests (pass by definition, test mocks, verify compiler-checked facts) = GAPS FOUND. </quick_reference>

<when_to_use>

• xpowers:executing-plans completed all tasks
• Before claiming work is complete
• Before xpowers:finishing-a-development-branch
• Want to verify implementation matches spec

Don't use for:

• Mid-implementation (use xpowers:executing-plans)
• Before all tasks done
• Code reviews of external PRs (this is self-review) </when_to_use>

<the_process>

Step 1: Load Epic Specification

Announce: "I'm using xpowers:review-implementation to verify implementation matches spec. Reviewing with Google Fellow-level scrutiny."

Get epic and tasks:

tm show bd-1          # Epic specification
tm dep tree bd-1      # Task tree
tm list --parent bd-1 # All tasks

Create TodoWrite tracker:

TodoWrite todos:
- Review bd-2: Task Name
- Review bd-3: Task Name
- Review bd-4: Task Name
- Compile findings and make decision

---

Step 2: Review Each Task

For each task:

A. Read Task Specification

tm show bd-3

Extract:

• Goal (what problem solved?)
• Success criteria (how verify done?)
• Implementation checklist (files/functions/tests)
• Key considerations (edge cases)
• Anti-patterns (prohibited patterns)

---

B. Run Automated Code Completeness Checks

# TODOs/FIXMEs without issue numbers
rg -i "todo|fixme" src/ tests/ || echo "✅ None"

# Stub implementations
rg "unimplemented!|todo!|unreachable!|panic!\(\"not implemented" src/ || echo "✅ None"

# Unsafe patterns in production
rg "\.unwrap\(\)|\.expect\(" src/ | grep -v "/tests/" || echo "✅ None"

# Ignored/skipped tests
rg "#\[ignore\]|#\[skip\]|\.skip\(\)" tests/ src/ || echo "✅ None"

---

B2. Dead Code and Refactoring Remnants Audit

Context: After refactoring, old code must be REMOVED, not kept as fallback. The canonical implementation is the new one. Old code is dead code.

Key principle: "Don't bother with unused code. Delete it before you try to improve anything."

Automated detection patterns:

# 1. Fallback/Legacy Code Detection
# Patterns indicating old code left behind:
rg -i "fallback|legacy|old_|_old|deprecated|obsolete" src/ || echo "✅ None"

# Conditional using old implementation:
rg -i "if.*use.*old|if.*legacy|if.*fallback|ENABLE_OLD|USE_LEGACY|FALLBACK_TO" src/ || echo "✅ None"

# "was:" or "previously:" comments (describing removed behavior):
rg -i "was:|previously:|used to|before refactor" src/ || echo "✅ None"

# 2. Unused Code Detection (Language-Specific)

# Rust - dead code warnings:
cargo build 2>&1 | grep -E "warning.*never used|warning.*dead_code" || echo "✅ None"

# TypeScript/JavaScript - unused exports (if eslint configured):
npx eslint --rule 'no-unused-vars: error' src/ 2>/dev/null || echo "Check manually"

# Swift - unused variables (SwiftLint):
swiftlint lint --reporter json 2>/dev/null | jq '.[] | select(.rule_id == "unused")' || echo "Check manually"

# Python - vulture if available:
vulture src/ --min-confidence 80 2>/dev/null || echo "vulture not installed, check manually"

# 3. Orphaned Tests Detection
# Find tests that reference functions/classes that no longer exist:
git diff main...HEAD --name-only | grep -E "(test|spec)" || echo "No test files changed"

# 4. Deprecation Remnants (should be REMOVED, not marked):
rg "@deprecated|#\[deprecated\]|// deprecated|DEPRECATED|@Deprecated" src/ || echo "✅ None"

# 5. Backwards Compatibility Shims (unless external API):
rg -i "backward.*compat|legacy.*support|shim|polyfill" src/ || echo "✅ None"

If any patterns found, investigate:

1. Fallback code: Why does old implementation still exist? Delete it.
2. Unused functions: Who calls this? If nobody, delete it.
3. Orphaned tests: Does tested functionality still exist? If not, delete test.
4. Deprecation markers: Remove now or create bd issue with removal date.
5. Backwards compat shims: Is this external API? If internal, delete shim.

Dead Code Audit Results Template:

#### Dead Code Audit Results

| Category | Pattern | Found | Location | Action |
|----------|---------|-------|----------|--------|
| Fallback code | `legacy\|old_\|fallback` | 0 | - | ✅ None |
| Unused functions | compiler warnings | 0 | - | ✅ None |
| Deprecation markers | `@deprecated` | 0 | - | ✅ None |
| Orphaned tests | tests for removed code | 0 | - | ✅ None |
| Backwards compat shims | `shim\|polyfill` | 0 | - | ✅ None |

**Verdict:** ✅ No dead code / ❌ Dead code found - refactoring incomplete

If dead code found: This is a GAP. Old code after refactoring = incomplete refactoring.

---

C. Run Quality Gates (via test-runner agent)

IMPORTANT: Use xpowers:test-runner agent to avoid context pollution.

Dispatch xpowers:test-runner: "Run: cargo test"
Dispatch xpowers:test-runner: "Run: cargo fmt --check"
Dispatch xpowers:test-runner: "Run: cargo clippy -- -D warnings"
Dispatch xpowers:test-runner: "Run: .git/hooks/pre-commit"

---

D. Read Implementation Files

CRITICAL: READ actual files, not just git diff.

# See changes
git diff main...HEAD -- src/auth/jwt.ts

# THEN READ FULL FILE
Read tool: src/auth/jwt.ts

While reading, check:

• ✅ Code implements checklist items (not stubs)
• ✅ Error handling uses proper patterns (Result, try/catch)
• ✅ Edge cases from "Key Considerations" handled
• ✅ Code is clear and maintainable
• ✅ No anti-patterns present

---

E. Code Quality Review (Google Fellow Perspective)

Assume code written by junior engineer. Apply production-grade scrutiny.

Error Handling:

• Proper use of Result/Option or try/catch?
• Error messages helpful for production debugging?
• No unwrap/expect in production?
• Errors propagate with context?
• Failure modes graceful?

Safety:

• No unsafe blocks without justification?
• Proper bounds checking?
• No potential panics?
• No data races?
• No SQL injection, XSS vulnerabilities?

Clarity:

• Would junior understand in 6 months?
• Single responsibility per function?
• Descriptive variable names?
• Complex logic explained?
• No clever tricks - obvious and boring?

Testing (CRITICAL - Apply strict scrutiny):

• Edge cases covered (empty, max, Unicode)?
• Tests catch real bugs, not just inflate coverage?
• Test names describe specific bug prevented?
• Tests test behavior, not implementation?
• Failure scenarios tested?
• No tautological tests (see Test Quality Audit below)?

Production Readiness:

• Comfortable deploying to production?
• Could cause outage or data loss?
• Performance acceptable under load?
• Logging sufficient for debugging?

---

E2. Test Quality Audit (Mandatory for All New Tests)

CRITICAL: Review every new/modified test for meaningfulness. Tautological tests are WORSE than no tests - they give false confidence.

For each test, ask:

1. What bug would this catch? → If you can't name a specific failure mode, test is pointless
2. Could production code break while this test passes? → If yes, test is too weak
3. Does this test a real user scenario? → Or just implementation details?
4. Is the assertion meaningful? → expect(result != nil) is weaker than expect(result == expectedValue)

Red flags (REJECT implementation until fixed):

• ❌ Tests that only verify syntax/existence ("enum has cases", "struct has fields")
• ❌ Tautological tests (pass by definition: expect(builder.build() != nil) when build() can't return nil)
• ❌ Tests that duplicate implementation (testing 1+1==2 by asserting 1+1==2)
• ❌ Tests without meaningful assertions (call code but don't verify outcomes matter)
• ❌ Tests that verify mock behavior instead of production code
• ❌ Codable/Equatable round-trip tests with only happy path data
• ❌ Generic test names ("test_basic", "test_it_works", "test_model")

Examples of meaningless tests to reject:

// ❌ REJECT: Tautological - compiler ensures enum has cases
func testEnumHasCases() {
    _ = MyEnum.caseOne  // This proves nothing
    _ = MyEnum.caseTwo
}

// ❌ REJECT: Tautological - build() returns non-optional, can't be nil
func testBuilderReturnsValue() {
    let result = Builder().build()
    #expect(result != nil)  // Always passes by type system
}

// ❌ REJECT: Tests mock, not production code
func testServiceCallsAPI() {
    let mock = MockAPI()
    let service = Service(api: mock)
    service.fetchData()
    #expect(mock.fetchCalled)  // Tests mock behavior, not real logic
}

// ❌ REJECT: Happy path only, no edge cases
func testCodable() {
    let original = User(name: "John", age: 30)
    let data = try! encoder.encode(original)
    let decoded = try! decoder.decode(User.self, from: data)
    #expect(decoded == original)  // What about empty name? Max age? Unicode?
}

Examples of meaningful tests to approve:

// ✅ APPROVE: Catches missing validation bug
func testEmptyPayloadReturnsValidationError() {
    let result = validator.validate(payload: "")
    #expect(result == .error(.emptyPayload))
}

// ✅ APPROVE: Catches race condition bug
func testConcurrentWritesDontCorruptData() {
    let store = ThreadSafeStore()
    DispatchQueue.concurrentPerform(iterations: 1000) { i in
        store.write(key: "k\(i)", value: i)
    }
    #expect(store.count == 1000)  // Would fail if race condition exists
}

// ✅ APPROVE: Catches error handling bug
func testMalformedJSONReturns400Not500() {
    let response = api.parse(json: "{invalid")
    #expect(response.status == 400)  // Not 500 which would indicate unhandled exception
}

// ✅ APPROVE: Catches encoding bug with edge case
func testUnicodeNamePreservedAfterRoundtrip() {
    let original = User(name: "日本語テスト 🎉")
    let decoded = roundtrip(original)
    #expect(decoded.name == original.name)
}

Audit process:

# Find all new/modified test files
git diff main...HEAD --name-only | grep -E "(test|spec)"

# Read each test file
Read tool: tests/new_feature_test.swift

# For EACH test function, document:
# - Test name
# - What bug it catches (or "TAUTOLOGICAL" if none)
# - Verdict: ✅ Keep / ⚠️ Strengthen / ❌ Remove/Replace

If tautological tests found:

## Test Quality Audit: GAPS FOUND ❌

### Tautological/Meaningless Tests
| Test | Problem | Action |
|------|---------|--------|
| testEnumHasCases | Compiler already ensures this | ❌ Remove |
| testBuilderReturns | Non-optional return, can't be nil | ❌ Remove |
| testCodable | Happy path only, no edge cases | ⚠️ Add: empty, unicode, max values |
| testServiceCalls | Tests mock, not production | ❌ Replace with integration test |

**Cannot approve until tests are meaningful.**

---

F. Verify Success Criteria with Evidence

For EACH criterion in bd task:

• Run verification command
• Check actual output
• Don't assume - verify with evidence
• Use xpowers:test-runner for tests/lints

Example:

Criterion: "All tests passing"
Command: cargo test
Evidence: "127 tests passed, 0 failures"
Result: ✅ Met

Criterion: "No unwrap in production"
Command: rg "\.unwrap\(\)" src/
Evidence: "No matches"
Result: ✅ Met

---

G. Check Anti-Patterns

Search for each prohibited pattern from bd task:

# Example anti-patterns from task
rg "\.unwrap\(\)" src/  # If task prohibits unwrap
rg "TODO" src/          # If task prohibits untracked TODOs
rg "\.skip\(\)" tests/  # If task prohibits skipped tests

---

H. Verify Key Considerations

Read code to confirm edge cases handled:

• Empty input validation
• Unicode handling
• Concurrent access
• Failure modes
• Performance concerns

Example: Task says "Must handle empty payload" → Find validation code for empty payload.

---

I. Record Findings

### Task: bd-3 - Implement JWT authentication

#### Evidence-Based Findings

| Criterion | Status | Confidence | Evidence |
|-----------|--------|------------|----------|
| All tests pass | ✅ Met | 1.0 | `cargo test`: 127 passed |
| Pre-commit passes | ❌ Not met | 1.0 | `cargo clippy`: 3 warnings |
| No unwrap in production | ❌ Not met | 1.0 | `rg "\.unwrap()"`: src/auth/jwt.ts:45 |

#### File Evidence
| File | Line | What Verified | Confidence |
|------|------|---------------|------------|
| src/auth/jwt.ts | 45 | unwrap violation | 1.0 |
| src/auth/jwt.ts | 12-30 | token generation logic | 0.9 |

**Findings below 0.8:** None (all verified)

#### Automated Checks
- TODOs: ✅ None
- Stubs: ✅ None
- Unsafe patterns: ❌ Found `.unwrap()` at src/auth/jwt.ts:45
- Ignored tests: ✅ None

#### Quality Gates
- Tests: ✅ Pass (127 tests)
- Formatting: ✅ Pass
- Linting: ❌ 3 warnings
- Pre-commit: ❌ Fails due to linting

#### Files Reviewed
- src/auth/jwt.ts: ⚠️ Contains `.unwrap()` at line 45
- tests/auth/jwt_test.rs: ✅ Complete

#### Code Quality
- Error Handling: ⚠️ Uses unwrap instead of proper error propagation
- Safety: ✅ Good
- Clarity: ✅ Good
- Testing: See Test Quality Audit below

#### Test Quality Audit (New/Modified Tests)
| Test | Bug It Catches | Verdict |
|------|----------------|---------|
| test_valid_token_accepted | Missing validation | ✅ Keep |
| test_expired_token_rejected | Expiration bypass | ✅ Keep |
| test_jwt_struct_exists | Nothing (tautological) | ❌ Remove |
| test_encode_decode | Encoding bug (but happy path only) | ⚠️ Add edge cases |

**Tautological tests found:** 1 (test_jwt_struct_exists)
**Weak tests found:** 1 (test_encode_decode needs edge cases)

#### Anti-Patterns
- "NO unwrap in production": ❌ Violated at src/auth/jwt.ts:45

#### Issues
**Critical:**
1. unwrap() at jwt.ts:45 - violates anti-pattern, must use proper error handling
2. Tautological test: test_jwt_struct_exists must be removed

**Important:**
3. 3 clippy warnings block pre-commit hook
4. test_encode_decode needs edge cases (empty, unicode, max length)

---

J. Mark Task Reviewed (TodoWrite)

---

Step 3: Report Findings

After reviewing ALL tasks:

If NO gaps:

## Implementation Review: APPROVED ✅

Reviewed bd-1 (OAuth Authentication) against implementation.

### Tasks Reviewed
- bd-2: Configure OAuth provider ✅
- bd-3: Implement token exchange ✅
- bd-4: Add refresh logic ✅

### Verification Summary
- All success criteria verified
- No anti-patterns detected
- All key considerations addressed
- All files implemented per spec

### Evidence
- Tests: 127 passed, 0 failures (2.3s)
- Linting: No warnings
- Pre-commit: Pass
- Code review: Production-ready

Ready to proceed to xpowers:finishing-a-development-branch.

If gaps found:

## Implementation Review: GAPS FOUND ❌

Reviewed bd-1 (OAuth Authentication) against implementation.

### Tasks with Gaps

#### bd-3: Implement token exchange
**Gaps:**
- ❌ Success criterion not met: "Pre-commit hooks pass"
  - Evidence: cargo clippy shows 3 warnings
- ❌ Anti-pattern violation: Found `.unwrap()` at src/auth/jwt.ts:45
- ⚠️ Key consideration not addressed: "Empty payload validation"
  - No check for empty payload in generateToken()

#### bd-4: Add refresh logic
**Gaps:**
- ❌ Success criterion not met: "All tests passing"
  - Evidence: test_verify_expired_token failing

### Cannot Proceed
Implementation does not match spec. Fix gaps before completing.

---

Step 4: Gate Decision

If APPROVED:

Announce: "I'm using xpowers:finishing-a-development-branch to complete this work."

Use Skill tool: xpowers:finishing-a-development-branch

If GAPS FOUND:

STOP. Do not proceed to finishing-a-development-branch.
Fix gaps or discuss with partner.
Re-run review after fixes.

</the_process>

Developer only checks git diff, doesn't read actual files # Review process git diff main...HEAD # Shows changes

Developer sees:

• function generateToken(payload) {
• return jwt.sign(payload, secret);
• }

Approves based on diff

"Looks good, token generation implemented ✅"

Misses: Full context shows no validation

function generateToken(payload) { // No validation of payload! // No check for empty payload (key consideration) // No error handling if jwt.sign fails return jwt.sign(payload, secret); }

<why_it_fails>

• Git diff shows additions, not full context
• Missed that empty payload not validated (key consideration)
• Missed that error handling missing (quality issue)
• False approval - gaps exist but not caught
• Will fail in production when empty payload passed </why_it_fails>

**Correct review process:**

# See changes
git diff main...HEAD -- src/auth/jwt.ts

# THEN READ FULL FILE
Read tool: src/auth/jwt.ts

Reading full file reveals:

function generateToken(payload) {
  // Missing: empty payload check (key consideration from bd task)
  // Missing: error handling for jwt.sign failure
  return jwt.sign(payload, secret);
}

Record in findings:

⚠️ Key consideration not addressed: "Empty payload validation"
- No check for empty payload in generateToken()
- Code at src/auth/jwt.ts:15-17

⚠️ Error handling: jwt.sign can throw, not handled

What you gain:

• Caught gaps that git diff missed
• Full context reveals missing validation
• Quality issues identified before production
• Spec compliance verified, not assumed

Developer assumes tests passing means done # Run tests cargo test # Output: 127 tests passed

Developer concludes

"Tests pass, implementation complete ✅"

Proceeds to finishing-a-development-branch

Misses:

• bd task has 5 success criteria
• Only checked 1 (tests pass)
• Anti-pattern: unwrap() present (prohibited)
• Key consideration: Unicode handling not tested
• Linter has warnings (blocks pre-commit)

<why_it_fails>

• Tests passing ≠ spec compliance
• Didn't verify all success criteria
• Didn't check anti-patterns
• Didn't verify key considerations
• Pre-commit will fail (blocks merge)
• Ships code violating anti-patterns </why_it_fails>

**Correct review checks ALL criteria:**

bd task has 5 success criteria:
1. "All tests pass" ✅ - Evidence: 127 passed
2. "Pre-commit passes" ❌ - Evidence: clippy warns (3 warnings)
3. "No unwrap in production" ❌ - Evidence: Found at jwt.ts:45
4. "Unicode handling tested" ⚠️ - Need to verify test exists
5. "Rate limiting implemented" ⚠️ - Need to check code

Result: 1/5 criteria verified met. GAPS EXIST.

Run additional checks:

# Check criterion 2
cargo clippy
# 3 warnings found ❌

# Check criterion 3
rg "\.unwrap\(\)" src/
# src/auth/jwt.ts:45 ❌

# Check criterion 4
rg "unicode" tests/
# No matches ⚠️ Need to verify

Decision: GAPS FOUND, cannot proceed

What you gain:

• Verified ALL criteria, not just tests
• Caught anti-pattern violations
• Caught pre-commit blockers
• Prevented shipping non-compliant code
• Spec contract honored completely

Developer rationalizes skipping rigor for "simple" task bd task: "Add logging to error paths"

Developer thinks: "Simple task, just added console.log"

Skips:

• Automated checks (assumes no issues)
• Code quality review (seems obvious)
• Full success criteria verification

Approves quickly:

"Logging added ✅"

Misses:

• console.log used instead of proper logger (anti-pattern)
• Only added to 2 of 5 error paths (incomplete)
• No test verifying logs actually output (criterion)
• Logs contain sensitive data (security issue)

<why_it_fails>

• "Simple" tasks have hidden complexity
• Skipped rigor catches exactly these issues
• Incomplete implementation (2/5 paths)
• Security vulnerability shipped
• Anti-pattern not caught
• Failed success criterion (test logs) </why_it_fails>

**Follow full review process:**

# Automated checks
rg "console\.log" src/
# Found at error-handler.ts:12, 15 ⚠️

# Read bd task
tm show bd-5

# Success criteria:
# 1. "All error paths logged"
# 2. "No sensitive data in logs"
# 3. "Test verifies log output"

# Check criterion 1
grep -n "throw new Error" src/
# 5 locations found
# Only 2 have logging ❌ Incomplete

# Check criterion 2
Read tool: src/error-handler.ts
# Logs contain password field ❌ Security issue

# Check criterion 3
rg "test.*log" tests/
# No matches ❌ Test missing

Decision: GAPS FOUND

• Incomplete (3/5 error paths missing logs)
• Security issue (logs password)
• Anti-pattern (console.log instead of logger)
• Missing test

What you gain:

• "Simple" task revealed multiple gaps
• Security vulnerability caught pre-production
• Rigor prevents incomplete work shipping
• All criteria must be met, no exceptions

Developer approves implementation with high test coverage but tautological tests # Test results show good coverage cargo test # 45 tests passed ✅ # Coverage: 92% ✅

Developer approves based on numbers

"Tests pass with 92% coverage, implementation complete ✅"

Proceeds to finishing-a-development-branch

Later in production:

- Validation bypassed because test only checked "validator exists"

- Race condition because test only checked "lock was acquired"

- Encoding corruption because test only checked "encode != nil"

<why_it_fails>

• High coverage doesn't mean meaningful tests
• Tests verified existence/syntax, not behavior
• Tautological tests passed by definition:
  • expect(validator != nil) - always passes, doesn't test validation logic
  • expect(lock.acquire()) - tests mock, not thread safety
  • expect(encoded.count > 0) - tests non-empty, not correctness
• Production bugs occurred despite "good" test coverage
• Coverage metrics were gamed with meaningless tests </why_it_fails>

**Audit each test for meaningfulness:**

# Find new tests
git diff main...HEAD --name-only | grep test

# Read and audit each test
Read tool: tests/validator_test.swift

For each test, document:

#### Test Quality Audit

| Test | Assertion | Bug Caught? | Verdict |
|------|-----------|-------------|---------|
| testValidatorExists | `!= nil` | ❌ None (compiler checks) | ❌ Remove |
| testValidInput | `isValid == true` | ⚠️ Happy path only | ⚠️ Add edge cases |
| testEmptyInputFails | `isValid == false` | ✅ Missing validation | ✅ Keep |
| testLockAcquired | mock.acquireCalled | ❌ Tests mock | ❌ Replace |
| testConcurrentAccess | count == expected | ✅ Race condition | ✅ Keep |
| testEncodeNotNil | `!= nil` | ❌ Type guarantees this | ❌ Remove |
| testUnicodeRoundtrip | decoded == original | ✅ Encoding corruption | ✅ Keep |

**Tautological tests:** 3 (must remove)
**Weak tests:** 1 (must strengthen)
**Meaningful tests:** 3 (keep)

Decision: GAPS FOUND ❌

## Test Quality Audit: GAPS FOUND

### Tautological Tests (Must Remove)
- testValidatorExists: Compiler ensures non-nil, test proves nothing
- testLockAcquired: Tests mock behavior, not actual thread safety
- testEncodeNotNil: Return type is non-optional, can never be nil

### Weak Tests (Must Strengthen)
- testValidInput: Only happy path, add:
  - testEmptyStringRejected
  - testMaxLengthRejected
  - testUnicodeNormalized

### Action Required
Remove 3 tautological tests, add 3 edge case tests, then re-review.

What you gain:

• Real test quality, not coverage theater
• Bugs caught before production
• Tests that actually verify behavior
• Confidence in test suite

Developer completes refactoring but leaves old implementation as fallback # After refactoring auth system: git diff shows: + function authenticateV2(token) { ... } # New implementation function authenticate(token) { ... } # Old still exists! function authenticateLegacy(token) { ... } # Even older!

In config:

const USE_LEGACY_AUTH = process.env.LEGACY_AUTH ?? true

Developer claims: "Refactoring complete"

<why_it_fails>

• Old implementations still present (authenticate, authenticateLegacy)
• Feature flag enables fallback to old code
• Tests may still use old functions
• No single canonical implementation
• Technical debt increased, not decreased
• "Refactoring" actually added code instead of replacing </why_it_fails>

**Run dead code audit:**

# Fallback patterns
rg -i "legacy|old_|fallback" src/
# Found: authenticateLegacy, USE_LEGACY_AUTH ❌

# Check callers
rg "authenticate\(" src/ --type ts
# authenticate: 0 callers ❌ DEAD
# authenticateLegacy: 0 callers ❌ DEAD
# authenticateV2: 15 callers ✅ ACTIVE

Dead Code Audit Results:

Category	Pattern	Found	Location	Action
Fallback code	legacy|fallback	2	auth.ts:45,89	❌ Delete
Unused functions	no callers	2	authenticate(), authenticateLegacy()	❌ Delete
Feature flags	USE_LEGACY	1	config.ts:12	❌ Delete

Decision: GAPS FOUND ❌

## Dead Code Audit: GAPS FOUND

### Refactoring Remnants
- authenticate() at auth.ts:12 - 0 callers, delete
- authenticateLegacy() at auth.ts:45 - 0 callers, delete
- USE_LEGACY_AUTH flag at config.ts:12 - enables dead code, delete

### Required Actions
1. Delete authenticate() - replaced by authenticateV2()
2. Delete authenticateLegacy() - obsolete
3. Delete USE_LEGACY_AUTH flag - no longer needed
4. Rename authenticateV2() to authenticate() (cleaner API)
5. Update/delete tests for removed functions

**Cannot approve until old code is removed.**

What you gain:

• Single canonical implementation
• No dead code accumulation
• Tests test actual functionality
• Technical debt reduced, not increased
• Refactoring actually complete

<critical_rules>

Rules That Have No Exceptions

1. Review every task → No skipping "simple" tasks
2. Run all automated checks → TODOs, stubs, unwrap, ignored tests
3. Run dead code audit → Fallback code, unused functions, deprecation markers
4. Read actual files with Read tool → Not just git diff
5. Verify every success criterion → With evidence, not assumptions
6. Check all anti-patterns → Search for prohibited patterns
7. Apply Google Fellow scrutiny → Production-grade code review
8. Audit all new tests for meaningfulness → Tautological tests = gaps, not coverage
9. If gaps found → STOP → Don't proceed to finishing-a-development-branch

Common Excuses

All of these mean: STOP. Follow full review process.

• "Tests pass, must be complete" (Tests ≠ spec, check all criteria)
• "I implemented it, it's done" (Implementation ≠ compliance, verify)
• "No time for thorough review" (Gaps later cost more than review now)
• "Looks good to me" (Opinion ≠ evidence, run verifications)
• "Small gaps don't matter" (Spec is contract, all criteria matter)
• "Will fix in next PR" (This PR completes this epic, fix now)
• "Can check diff instead of files" (Diff shows changes, not context)
• "Automated checks cover it" (Checks + code review both required)
• "Success criteria passing means done" (Also check anti-patterns, quality, edge cases)
• "Tests exist, so testing is complete" (Tautological tests = false confidence)
• "Coverage looks good" (Coverage can be gamed with meaningless tests)
• "Tests are boilerplate, don't need review" (Every test must catch a real bug)
• "It's just a simple existence check" (Compiler already checks existence)
• "Keeping old code as fallback is safe" (Old code = dead code, delete it)
• "We might need the old implementation later" (Version control remembers, delete now)
• "Backwards compatibility requires the shim" (Internal code doesn't need backwards compat)
• "Deprecation marker is enough" (Deprecation = "delete soon", not "keep forever")
• "The old tests still pass" (Tests for removed code = orphaned tests, delete)

</critical_rules>

<verification_checklist> Before approving implementation:

Per task:

• Read bd task specification completely
• Ran all automated checks (TODOs, stubs, unwrap, ignored tests)
• Ran dead code audit (fallback patterns, unused code, deprecation, orphaned tests)
• Ran all quality gates via test-runner agent (tests, format, lint, pre-commit)
• Read actual implementation files with Read tool (not just diff)
• Reviewed code quality with Google Fellow perspective
• Audited all new tests for meaningfulness (not tautological)
• Verified every success criterion with evidence
• Checked every anti-pattern (searched for prohibited patterns)
• Verified every key consideration addressed in code

Overall:

• Reviewed ALL tasks (no exceptions)
• TodoWrite tracker shows all tasks reviewed
• Compiled findings (approved or gaps)
• If approved: all criteria met for all tasks
• If gaps: documented exactly what missing

Can't check all boxes? Return to Step 2 and complete review. </verification_checklist>

**This skill is called by:** - xpowers:executing-plans (Step 5, after all tasks executed)

This skill calls:

• xpowers:finishing-a-development-branch (if approved)
• xpowers:test-runner agent (for quality gates)

This skill uses:

• xpowers:verification-before-completion principles (evidence before claims)

Call chain:

xpowers:executing-plans → xpowers:review-implementation → xpowers:finishing-a-development-branch
                         ↓
                   (if gaps: STOP)

CRITICAL: Use tm commands (tm show, tm list, tm dep tree), never read .beads/issues.jsonl directly.

**Detailed guides:** - [Code quality standards by language](resources/quality-standards.md) - [Common anti-patterns to check](resources/anti-patterns-reference.md) - [Production readiness checklist](resources/production-checklist.md)

When stuck:

• Unsure if gap critical → If violates criterion, it's a gap
• Criteria ambiguous → Ask user for clarification before approving
• Anti-pattern unclear → Search for it, document if found
• Quality concern → Document as gap, don't rationalize away