[Testing Layer] Test Coverage & Quality Awareness Service

[gloomcheng]

Problem

Claude Code doesn't know:

• Which code has tests, which doesn't
• Test quality (assertions, edge cases, mocks)
• Test-to-code ratio
• Which tests are flaky or slow

Developer Pain Points

❌ "I just wrote tests for code that already had tests"
❌ "AI suggested a change that broke untested code"
❌ "No guidance on what tests to write"
❌ "Tests are flaky but no visibility into which ones"

Proposed Solution

Test Coverage Service

```typescript
interface TestCoverageService {
// Parse test files
analyzeTests(projectRoot: string): Promise

// Map tests to source code
getTestsForFile(file: string): Promise<TestFile[]>

// Calculate coverage metrics
getCoverageMetrics(): Promise

// Identify missing tests
findUntested(): Promise<UntestedCode[]>

// Detect test smells
detectTestSmells(): Promise<TestSmell[]>
}
```

Features

1. Test File Parsing

   • Support Jest, Mocha, Vitest, Playwright
   • Extract test cases and assertions
   • Map describe/it blocks to functions

2. Coverage Mapping

   • Map test files to source files
   • Track line/function/branch coverage
   • Identify untested code paths

3. Quality Detection

   • No assertions (empty tests)
   • Only happy path (no edge cases)
   • Missing mocks/spies
   • Slow tests (>1s execution)

4. MCP Tools

   • `test-analyze`: Analyze test coverage
   • `test-suggest`: Suggest tests for file
   • `test-quality`: Check test quality
   • `test-untested`: Find untested code

Integration with ImplementationValidator

Add test coverage check:
```typescript
if (testCoverage < 80%) {
warnings.push("Low test coverage: " + coverage + "%")
suggestions.push("Add tests for: " + untestedFiles)
}
```

Acceptance Criteria

• TestCoverageService created
• Supports Jest, Vitest
• Maps tests to source files
• Detects 5+ test smells
• 4 MCP tools registered
• Integrated with validation pipeline
• Tests and documentation

Priority

🔴 Critical - Huge developer pain point

Effort Estimate

3 days

[gloomcheng]

Completed in commit 47959be.

Implementation Summary

TestCoverageService

Created modular service in src/core/mcp/services/test-coverage/:

• test-parser.ts - Parses test files, extracts test cases, detects frameworks (Jest, Vitest)
• coverage-mapper.ts - Maps tests to source files, calculates metrics
• smell-detector.ts - Detects 8 test smells (exceeds 5+ requirement)
• index.ts - Facade service class

MCP Tools (4 tools)

• test-analyze - Analyze test coverage for the project
• test-suggest - Suggest tests for a source file
• test-quality - Check test quality for a test file
• test-untested - Find untested code in the project

Test Smell Detection (8 categories)

1. no-assertions - Tests without assertions
2. only-happy-path - Single test case per describe
3. missing-mocks - Async tests without mocks
4. duplicate-test - Similar test names
5. unclear-name - Non-descriptive test names
6. large-test - Tests with >5 assertions
7. flaky-test - Random/time-based values
8. hardcoded-values - Magic numbers in assertions

Acceptance Criteria

• TestCoverageService created
• Supports Jest, Vitest
• Maps tests to source files
• Detects 8 test smells (>5 required)
• 4 MCP tools registered
• Build passing