test-driven-development

Test-driven development in TypeScript is practiced by writing a failing unit test first, running it to ensure failure, then implementing minimal production code to pass, and finally refactoring. This enforces a strict test-first workflow to guard against regressions.

The red-green-refactor cycle in software testing involves writing a failing test (red), writing the minimal code required to make that test pass (green), and then cleaning up the code without changing its behavior (refactor).

You need a test framework like Jest to enforce a test-first workflow. The practice requires running failing tests before implementing production code, so an environment capable of executing JavaScript or TypeScript test suites is necessary.

Test-driven development is highly effective for bug fixes and refactoring. You write a failing test that reproduces the bug or verifies the refactored behavior, then implement the code changes until all tests pass, ensuring safe modifications.

The best way to start writing failing tests before production code is to define a clear test-first workflow. Run the failing test to confirm it fails for the expected reason, implement the minimal logic to satisfy it, and repeat until all tests pass.