Write Tests

Write Unit Tests

Create comprehensive unit tests with proper imports and setup according to project testing conventions.

Usage

/write-tests [target]

Target (optional):

• If not specified: tests cover the diff between current branch and main
• If specified: tests cover the specified file or module

Examples:

/write-tests                                    # Test all changes vs main
/write-tests src/core/query.py                  # Test specific file

What It Does

1. Test Coverage

• Tests all public methods and functions
• Covers edge cases and error conditions
• Tests both positive and negative scenarios
• Aims for high code coverage

2. Test Structure

• Uses project's testing framework conventions
• Writes clear, descriptive test names
• Follows Arrange-Act-Assert pattern
• Groups related tests logically

3. Test Cases Include

• Happy path scenarios
• Edge cases and boundary conditions
• Error handling and exception cases
• Appropriate mocking of external dependencies

4. Test Quality

• Tests are independent and isolated
• Tests are deterministic and repeatable
• Tests are simple and focused
• Helpful assertion messages included
• No external dependencies (database fixtures, files, APIs)

Project-Specific Conventions

Backend (pytest):

• Location: tests/unit/ or tests/integration/ (follow project conventions)
• Fixtures in conftest.py
• Use real objects (not mocks) except for LLM calls
• Auto-marked by directory (unit vs integration)

Frontend (Jest/Vitest):

• Location: __tests__/ mirroring src/ structure
• Mocks in __mocks__/
• Share mocking functions in testUtils.ts
• Mock all external API calls

Style:

• Arrange-Act-Assert pattern
• Descriptive test names (test_method_condition_expected_result)
• No testing for specific UI strings
• Isolated and deterministic

What NOT to Do (Anti-Patterns)

The Iron Laws

1. NEVER test mock behavior
2. NEVER add test-only methods to production classes
3. NEVER mock without understanding dependencies

Anti-Pattern 1: Testing Mock Behavior

Bad:

// Testing that mock exists, not real behavior
test('renders sidebar', () => {
  render(<Page />);
  expect(screen.getByTestId('sidebar-mock')).toBeInTheDocument();
});

Fix: Test real component or don't mock it. If you must mock, don't assert on mock elements.

Anti-Pattern 2: Test-Only Methods in Production

Bad: Adding destroy() to a class only because tests need cleanup.

// BAD: destroy() only used in tests
class Session {
  async destroy() { /* cleanup */ }
}

// In tests
afterEach(() => session.destroy());

Fix: Put cleanup utilities in test-utils/, not production code.

// GOOD: Test utility
// test-utils/cleanup.ts
export async function cleanupSession(session: Session) {
  const workspace = session.getWorkspaceInfo();
  if (workspace) await workspaceManager.destroyWorkspace(workspace.id);
}

// In tests
afterEach(() => cleanupSession(session));

Anti-Pattern 3: Mocking Without Understanding

Bad: Mocking "to be safe" without understanding what the test depends on.

// Mock breaks test logic - method had side effects test needed!
vi.mock('ToolCatalog', () => ({
  discoverAndCacheTools: vi.fn().mockResolvedValue(undefined)
}));

await addServer(config);
await addServer(config);  // Should throw - but won't!

Fix: Run test with real implementation first, then add minimal mocking.

Anti-Pattern 4: Incomplete Mocks

Bad: Mocking only fields you think you need.

const mockResponse = {
  status: 'success',
  data: { userId: '123' }
  // Missing: metadata that downstream code uses
};

Fix: Mirror the complete real API response structure.

Red Flags

• Assertion checks for *-mock test IDs
• Methods only called in test files
• Mock setup is >50% of test
• "Mocking just to be safe"
• Test fails when you remove mock

Gate Function

Before each mock, ask: "Do I understand what this test actually needs?"

Notes

• Only write tests when explicitly requested
• Always run tests after creating them to verify they pass
• Use pytest for backend, npm test for frontend

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