testing

To write tests using TDD and AAA patterns, you follow the Red-Green-Refactor cycle and structure tests with Arrange, Act, Assert sections. This enforces test clarity by writing a failing test first, then implementing minimal code to pass, and refactoring for readability.

Unit, integration, and E2E test selection determines the verification level based on the feature scope. Unit tests verify individual components, integration tests check interactions between modules, and E2E tests validate complete user workflows across the entire system.

You should use TDD for bug fixes and behavior changes to ensure new changes are guardable with deterministic tests. Writing a failing test that reproduces the bug or verifies the new behavior first guarantees the subsequent code implementation resolves the exact issue.

You structure reliable test suites by enforcing strict naming conventions, deterministic execution, and clear failure signals. Using the AAA pattern isolates test logic into distinct arrangement, action, and assertion phases to improve long-term maintainability and readability.

The best way to start is to write a failing unit test for the new feature, implement the minimal code required to pass the test, and then refactor the implementation for readability. This Red-Green-Refactor cycle ensures the test accurately verifies the feature.

Integration tests fail non-deterministically when they lack clear failure signals or depend on uncontrolled external states. Enforcing the AAA pattern and ensuring deterministic execution by isolating the Arrange and Act phases prevents unpredictable test behavior and false failures.