test-driven-development

To start test-driven development, write a focused failing test that specifies the desired behavior, run it to confirm it fails for the right reasons, and implement minimal code to pass. This enforces a verifiable specification before production code is written.

The red-green-refactor workflow is a test-driven development cycle where you write a minimal failing test, implement the simplest code to pass, and then refactor while keeping tests green. This ensures code behavior is specified and verified automatically.

You can use mocking during test-first development, but you should prefer assertions against real behavior rather than mocks. The workflow includes anti-pattern guidance to avoid tests that assert mock behavior and to ensure test completeness.

Test-driven development works for fixing bugs and refactoring modules by enforcing a failing test that specifies desired behavior before implementing fixes. It applies to changing observable behavior in codebases where automated tests can be executed.

You need to observe a failing test before implementing production code to prove coverage and confirm the test fails for the right reasons. This validates that the behavior is correctly specified before writing the minimal code to pass.