test-coverage

Analyze test coverage, identify gaps, and recommend test improvements.

Triggers

"analyze test coverage"
"what's not tested"
"coverage report"
"find untested code"
"test gaps"
"coverage analysis"

Purpose

This skill provides comprehensive test coverage analysis by:

Parsing coverage reports from multiple formats
Identifying coverage gaps by priority
Mapping coverage to requirements
Recommending test additions
Tracking coverage trends over time

Behavior

When triggered, this skill:

Locates coverage data:
- Find coverage reports (lcov, cobertura, istanbul, etc.)
- Identify test directories and conventions
- Load historical coverage data
Analyzes coverage metrics:
- Line coverage percentage
- Branch coverage percentage
- Function coverage percentage
- File-level breakdown
Identifies critical gaps:
- Untested critical paths
- Low-coverage high-change files
- Untested public APIs
- Missing edge case coverage
Maps to requirements:
- Cross-reference with traceability data
- Identify untested requirements
- Flag coverage by priority
Generates recommendations:
- Prioritized list of tests to add
- Estimated effort per test
- Coverage improvement projection
Tracks trends:
- Coverage over time
- Coverage by component
- Impact of recent changes

Coverage Metrics

Line Coverage

line_coverage:
  description: Percentage of code lines executed by tests
  calculation: (lines_executed / total_lines) * 100
  targets:
    excellent: ">= 90%"
    good: ">= 80%"
    acceptable: ">= 70%"
    poor: "< 70%"

Branch Coverage

branch_coverage:
  description: Percentage of decision branches executed
  calculation: (branches_taken / total_branches) * 100
  targets:
    excellent: ">= 85%"
    good: ">= 75%"
    acceptable: ">= 65%"
    poor: "< 65%"
  importance: Critical for logic paths

Function Coverage

function_coverage:
  description: Percentage of functions called by tests
  calculation: (functions_called / total_functions) * 100
  targets:
    excellent: ">= 95%"
    good: ">= 90%"
    acceptable: ">= 80%"
    poor: "< 80%"

Statement Coverage

statement_coverage:
  description: Percentage of statements executed
  calculation: (statements_executed / total_statements) * 100
  note: Similar to line coverage but counts multi-statement lines

Coverage Report Format

# Test Coverage Analysis Report

**Date**: 2025-12-08
**Project**: User Service
**Analyzer**: test-coverage skill

## Executive Summary

| Metric | Current | Target | Status |
|--------|---------|--------|--------|
| Line Coverage | 78.5% | 80% | ⚠️ Below Target |
| Branch Coverage | 72.3% | 75% | ⚠️ Below Target |
| Function Coverage | 91.2% | 90% | ✅ Meets Target |
| Files with 0% | 3 | 0 | ❌ Action Required |

**Overall Assessment**: Coverage below targets in 2 of 4 metrics. Focus on branch coverage and untested files.

## Coverage by Component

| Component | Lines | Branches | Functions | Trend |
|-----------|-------|----------|-----------|-------|
| src/auth/ | 92% | 88% | 100% | ↑ +2% |
| src/user/ | 85% | 78% | 95% | → 0% |
| src/api/ | 76% | 68% | 88% | ↓ -3% |
| src/utils/ | 65% | 55% | 82% | → 0% |
| src/db/ | 58% | 45% | 75% | ↓ -5% |

## Critical Gaps

### Priority 1: Untested Files

Files with 0% coverage that require immediate attention:

| File | Lines | Risk | Action |
|------|-------|------|--------|
| src/db/migrations.ts | 145 | High | Add migration tests |
| src/api/webhooks.ts | 89 | High | Add webhook handler tests |
| src/utils/retry.ts | 42 | Medium | Add retry logic tests |

### Priority 2: Low-Coverage Critical Paths

Business-critical code with insufficient coverage:

| File | Current | Target | Gap | Critical Path |
|------|---------|--------|-----|---------------|
| src/auth/oauth.ts | 55% | 90% | 35% | User authentication |
| src/api/payments.ts | 62% | 90% | 28% | Payment processing |
| src/user/permissions.ts | 68% | 85% | 17% | Authorization |

### Priority 3: Branch Coverage Gaps

Files with low branch coverage (complex logic undertested):

| File | Branch % | Uncovered Branches | Example |
|------|----------|-------------------|---------|
| src/api/router.ts | 45% | 12 | Error handling paths |
| src/utils/validator.ts | 52% | 8 | Edge case validations |
| src/db/query-builder.ts | 48% | 15 | Query variations |

## Uncovered Code Analysis

### src/auth/oauth.ts (55% line coverage)

Lines not covered:

45-67: Token refresh error handling
89-112: OAuth provider fallback logic
134-145: Session invalidation edge cases

Recommended tests:

Test token refresh with expired token
Test provider unavailable fallback
Test concurrent session invalidation


### src/api/payments.ts (62% line coverage)

Lines not covered:

78-95: Payment retry logic
123-140: Refund edge cases
167-180: Currency conversion errors

Recommended tests:

Test payment retry with transient failure
Test partial refund scenarios
Test invalid currency handling


## Requirements Coverage

Cross-reference with traceability data:

| Requirement | Test Coverage | Status |
|-------------|---------------|--------|
| UC-001: User Login | 95% | ✅ Covered |
| UC-002: User Registration | 88% | ✅ Covered |
| UC-003: Password Reset | 45% | ⚠️ Partial |
| UC-004: OAuth Login | 55% | ⚠️ Partial |
| REQ-001: Input Validation | 78% | ⚠️ Partial |
| NFR-001: Performance | 30% | ❌ Insufficient |

## Test Recommendations

### High Priority (This Sprint)

| # | Test to Add | File | Est. Effort | Coverage Gain |
|---|-------------|------|-------------|---------------|
| 1 | OAuth token refresh tests | oauth.test.ts | 2h | +15% |
| 2 | Payment retry scenarios | payments.test.ts | 3h | +12% |
| 3 | Migration execution tests | migrations.test.ts | 4h | +100% (new) |
| 4 | Webhook handler tests | webhooks.test.ts | 2h | +100% (new) |

### Medium Priority (Next Sprint)

| # | Test to Add | File | Est. Effort | Coverage Gain |
|---|-------------|------|-------------|---------------|
| 5 | Permission edge cases | permissions.test.ts | 2h | +8% |
| 6 | Router error paths | router.test.ts | 3h | +20% branch |
| 7 | Validation edge cases | validator.test.ts | 2h | +15% branch |

### Projected Impact

If all high-priority tests added:
- Line coverage: 78.5% → 85.2% (+6.7%)
- Branch coverage: 72.3% → 79.1% (+6.8%)
- Untested files: 3 → 1

## Coverage Trends

### Last 30 Days

Week 1: 82.1% ────────────────────────── Week 2: 80.5% ──────────────────────── Week 3: 79.2% ────────────────────── Week 4: 78.5% ───────────────────── ↓ Declining trend


### By Sprint

| Sprint | Coverage | Change | Notes |
|--------|----------|--------|-------|
| Sprint 10 | 82.1% | - | Baseline |
| Sprint 11 | 80.5% | -1.6% | New auth module |
| Sprint 12 | 79.2% | -1.3% | Payment integration |
| Sprint 13 | 78.5% | -0.7% | API expansion |

**Trend Analysis**: Coverage declining due to new feature velocity without proportional test additions. Recommend test-first approach for new features.

## Action Plan

### Immediate (This Week)
- [ ] Add OAuth token refresh tests
- [ ] Add payment retry tests
- [ ] Set up coverage gates in CI (minimum 80%)

### Short-term (This Sprint)
- [ ] Create migration test suite
- [ ] Create webhook test suite
- [ ] Address UC-003 and UC-004 coverage gaps

### Ongoing
- [ ] Require tests with new feature PRs
- [ ] Weekly coverage review in standup
- [ ] Quarterly coverage target adjustment

## Configuration

Coverage thresholds for CI gates:

```yaml
coverage_gates:
  global:
    lines: 80
    branches: 75
    functions: 90
    statements: 80

  per_file:
    lines: 70
    branches: 65

  new_code:
    lines: 90
    branches: 85


## Usage Examples

### Full Coverage Analysis

User: "Analyze test coverage"

Skill executes:

Locate coverage reports
Parse metrics
Identify gaps
Generate recommendations

Output: "Test Coverage Analysis Complete

Overall: 78.5% line, 72.3% branch

Status: ⚠️ Below targets

Critical Findings:

3 files with 0% coverage
2 critical paths undertested
Branch coverage declining

Top Recommendations:

Add OAuth tests (+15% gain, 2h effort)
Add payment retry tests (+12% gain, 3h effort)
Add migration tests (new coverage, 4h effort)

Report: .aiwg/testing/coverage-analysis.md"


### Find Untested Code

User: "What's not tested in auth module?"

Skill analyzes:

src/auth/ directory
Identifies untested paths

Output: "Auth Module Coverage: 92% lines, 88% branches

Untested Code:

oauth.ts (lines 45-67)
- Token refresh error handling
- Test: expired token scenario
oauth.ts (lines 89-112)
- Provider fallback logic
- Test: provider timeout scenario
session.ts (lines 134-145)
- Session invalidation edge cases
- Test: concurrent invalidation

Recommended Test Additions:

3 test cases
Estimated: 3 hours
Expected gain: +8% coverage"


### Coverage Trend

User: "Coverage report over time"

Skill returns: "Coverage Trend (Last 4 Sprints):

Sprint 10: 82.1% ██████████████████████ Sprint 11: 80.5% █████████████████████ Sprint 12: 79.2% ████████████████████ Sprint 13: 78.5% ███████████████████ ↓ Declining (-3.6%)

Cause: New feature velocity outpacing test additions

Recommendation:

Enforce 90% coverage on new code
Add test task to feature tickets
Schedule 'test debt' sprint"


## Integration

This skill uses:
- `traceability-check`: Map coverage to requirements
- `project-awareness`: Identify test conventions
- `artifact-metadata`: Track coverage reports

## Agent Orchestration

```yaml
agents:
  analysis:
    agent: test-architect
    focus: Coverage analysis and strategy

  implementation:
    agent: test-engineer
    focus: Test recommendations and implementation

  review:
    agent: code-reviewer
    focus: Coverage quality assessment

Configuration

Coverage Tool Detection

coverage_tools:
  javascript:
    - istanbul/nyc: coverage/lcov.info
    - jest: coverage/coverage-final.json
    - c8: coverage/lcov.info

  python:
    - coverage.py: .coverage, coverage.xml
    - pytest-cov: coverage.xml

  java:
    - jacoco: target/site/jacoco/jacoco.xml
    - cobertura: target/site/cobertura/coverage.xml

  go:
    - go test: coverage.out

Priority Calculation

priority_factors:
  critical_path:
    weight: 3
    paths: [auth, payments, permissions]

  recent_changes:
    weight: 2
    lookback: 30 days

  complexity:
    weight: 1.5
    metric: cyclomatic_complexity

  bug_history:
    weight: 2
    source: issue_tracker

Output Locations

Coverage reports: .aiwg/testing/coverage/
Analysis reports: .aiwg/testing/coverage-analysis.md
Trends: .aiwg/testing/coverage-trends.json
Recommendations: .aiwg/testing/coverage-recommendations.md

References

Test strategy: .aiwg/testing/test-strategy.md
Traceability matrix: .aiwg/reports/traceability-matrix.csv
Coverage templates: templates/test/coverage-report-template.md

test-coverage

test-coverage

Triggers

Purpose

Behavior

Coverage Metrics

Line Coverage

Branch Coverage

Function Coverage

Statement Coverage

Coverage Report Format

Configuration

Coverage Tool Detection

Priority Calculation

Output Locations

References

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