test-driven-development

Test-driven development requires writing a failing unit test that encodes the desired behavior, then implementing the minimal production code to pass that test. This applies to new features, bug fixes, and API changes.

The best way to write regression tests for API changes is to define the expected behavior with a failing test before changing the public contract. This captures regressions early and preserves the contract during implementation.

Yes, you need a unit testing environment to apply TDD to software design. Writing failing tests first clarifies design and communicates intent, requiring a framework capable of encoding behavior before implementation.

Test-driven development helps debugging and quality assurance by enforcing tests before implementation, which reduces defects and ensures the public contract is preserved. Tests guide the change by defining the expected outcome.

TDD may not suit exploratory prototyping where behavior is undefined, as it requires specifying the expected outcome in a failing test before writing minimal production code to guide design and validation.