# Review Module Test Coverage Improvement Summary

## Overview

Added comprehensive integration tests for low-coverage review modules to significantly improve test coverage and code quality.

## Coverage Improvements

### Before
- `engine.py`: 9%
- `instructions.py`: 7%
- `pr_engine.py`: 9%

### After
- `engine.py`: **60%** (↑51%)
- `instructions.py`: **72%** (↑65%)
- `pr_engine.py`: **81%** (↑72%)

## Test Files Created

### 1. `tests/unit/review/test_review_engine.py` (23 tests)

Tests for `ReviewEngine` in `src/mcp_vector_search/analysis/review/engine.py`:

**Coverage:**
- ✅ `run_review()` returns `ReviewResult` with correct structure
- ✅ `run_review()` with `file_filter` parameter
- ✅ `run_review()` with `use_cache=False` bypasses cache
- ✅ `ReviewType` enum values match expected strings
- ✅ `REVIEW_SEARCH_QUERIES` has entries for all `ReviewType` values
- ✅ `_parse_findings_json()` handles JSON in code blocks, plain JSON, invalid JSON
- ✅ `_format_code_context()` returns non-empty string with code chunks
- ✅ `_format_kg_context()` formats knowledge graph relationships
- ✅ `_generate_summary()` produces correct summaries
- ✅ `_get_chunk_id()` with chunk_id attribute and fallback
- ✅ `_gather_kg_relationships()` graceful degradation without KG
- ✅ `_cache_findings()` caches findings per chunk

**Key Testing Patterns:**
- Mock external dependencies (search engine, LLM, KG)
- Test with empty results to avoid LLM calls
- Test JSON parsing edge cases
- Test enum completeness
- Test graceful degradation

### 2. `tests/unit/review/test_instructions.py` (26 tests)

Tests for `InstructionsLoader` in `src/mcp_vector_search/analysis/review/instructions.py`:

**Coverage:**
- ✅ `format_for_prompt()` returns non-empty string with defaults
- ✅ `discover_and_load()` finds standards from multiple sources
- ✅ `_extract_from_editorconfig()` parses indent_style and max_line_length
- ✅ `_extract_from_pyproject()` extracts ruff, mypy, black settings
- ✅ `_extract_from_markdown()` extracts bullet points from sections
- ✅ `_extract_from_language_configs()` detects TypeScript, Ruby configs
- ✅ `_load_from_file()` loads and validates YAML config
- ✅ Missing files handled gracefully (no exceptions)
- ✅ `sources_found` list tracks which files were used
- ✅ Multiple sources merged correctly
- ✅ Deduplication within categories
- ✅ Fallback to defaults when no files found

**Key Testing Patterns:**
- Use `tmp_path` fixture for temporary config files
- Test both explicit config and auto-discovery
- Test graceful handling of missing/invalid files
- Test merge/deduplication logic
- Test file format parsers (TOML, YAML, INI, Markdown)

### 3. `tests/unit/review/test_pr_engine.py` (30 tests)

Tests for `PRReviewEngine` in `src/mcp_vector_search/analysis/review/pr_engine.py`:

**Coverage:**
- ✅ `PRReviewEngine` initializes correctly
- ✅ `_build_language_context()` returns language-specific content
- ✅ `_build_language_context()` handles multiple languages
- ✅ `_parse_git_diff()` correctly splits unified diff into `PRFilePatch` objects
- ✅ `review_pr()` with empty patches returns valid `PRReviewResult`
- ✅ `_generate_verdict()` returns correct verdict for blocking/non-blocking issues
- ✅ `_generate_summary()` produces correct summaries
- ✅ `_parse_comments_json()` handles JSON in code blocks, plain JSON, invalid JSON
- ✅ `_extract_function_names()` extracts Python, JavaScript function names
- ✅ `_gather_file_contexts()` skips deleted files
- ✅ `_gather_file_contexts()` includes related files from search
- ✅ `_format_file_contexts()` truncates large diffs
- ✅ Custom instructions override default instructions
- ✅ Immutability of frozen dataclasses (`PRFilePatch`, `PRContext`, etc.)

**Key Testing Patterns:**
- Mock search engine and LLM client
- Test with empty patches to avoid LLM calls
- Test verdict calculation logic
- Test JSON parsing edge cases
- Test language detection and context building
- Test immutability of data models

## Test Characteristics

### Fast Execution
- All tests complete in ~7 seconds (79 tests)
- No real file I/O except `tmp_path`
- Mock all external dependencies
- Use `pytest.mark.asyncio` for async tests

### Mock Strategy
```python
@pytest.fixture
def mock_search_engine():
    """Create a mock search engine."""
    mock = AsyncMock()
    mock.search = AsyncMock(return_value=[])
    return mock

@pytest.fixture
def mock_llm_client():
    """Create a mock LLM client."""
    mock = MagicMock()
    mock.model = "test-model"
    mock._chat_completion = AsyncMock(
        return_value={"choices": [{"message": {"content": "[]"}}]}
    )
    return mock
```

### Edge Cases Covered
- Empty inputs
- Invalid JSON
- Missing files
- Multiple languages
- Deleted files
- Large diffs (truncation)
- Invalid YAML
- Immutable dataclasses

## Running the Tests

```bash
# Run all review unit tests
uv run pytest tests/unit/review/ -v

# Run specific test file
uv run pytest tests/unit/review/test_review_engine.py -v

# Run with coverage report
uv run pytest tests/unit/review/ --cov=src/mcp_vector_search/analysis/review --cov-report=term-missing

# Run specific test
uv run pytest tests/unit/review/test_instructions.py::test_extract_from_editorconfig -v
```

## Test Results

```
============================== 79 passed in 6.72s ==============================
```

All 79 tests pass successfully with significant coverage improvements.

## Benefits

1. **Increased Confidence**: Higher test coverage means more reliable code
2. **Regression Prevention**: Tests catch bugs before they reach production
3. **Documentation**: Tests serve as usage examples
4. **Refactoring Safety**: Tests enable safe refactoring
5. **Fast Feedback**: Tests run in seconds, not minutes

## Next Steps

To further improve coverage:
1. Add integration tests that don't mock LLM calls (use real LLM)
2. Add end-to-end tests for full PR review workflow
3. Add performance tests for large codebases
4. Add tests for cache eviction and cleanup
5. Add tests for concurrent review requests

## Files Changed

- ✅ Created `tests/unit/review/__init__.py`
- ✅ Created `tests/unit/review/test_review_engine.py` (23 tests)
- ✅ Created `tests/unit/review/test_instructions.py` (26 tests)
- ✅ Created `tests/unit/review/test_pr_engine.py` (30 tests)

Total: 79 new tests, 3 new test files
