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README
Testing Anti-Patterns
Overview
Tests must verify real behavior, not mock behavior. Mocks are a means to isolate, not the thing being tested.
Core principle: Test what the code does, not what the mocks do.
Following strict TDD prevents these 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
The violation:
// ❌ BAD: Testing that the mock exists
test('renders sidebar', () => {
render(<Page />);
expect(screen.getByTestId('sidebar-mock')).toBeInTheDocument();
});
Why this is wrong:
This is the opening of the README. Read the full README on GitHub.