tdd

Test-driven development reduces fragile test suites by focusing on behavior verified through public interfaces. This approach ensures tests describe observable outcomes rather than internal calls, keeping them stable during refactoring.

The red-green-refactor loop is a test-driven development cycle where you write one failing test for a small behavior, implement minimal code to pass it, then refactor safely. It uses tracer bullets to build features incrementally.

Start test-driven development by writing a tracer-bullet test for the next public behavior using a vertical slice, then implement just enough code to make that test pass. Repeat the red-green-refactor loop for each new behavior.

Integration testing in this test-driven approach avoids mocking internal collaborators. It validates public interfaces and observable outcomes instead of internal calls, ensuring tests accurately describe system behavior without coupling.

Horizontal slicing in test-driven development means writing many tests before adding minimal implementation, creating implementation coupling. It is prevented by focusing on one small behavior at a time through vertical slices and tracer bullets.

Test-driven development works for both feature development and bug fixing. It applies the red-green-refactor loop with tracer bullets to write behavior-focused tests that clearly describe what the system does in either scenario.