test-driven-development
Guides development using the test-driven red-green-refactor loop, writing failing tests first to prove code works and reproduce bugs before fixing them.
What it does
Drives development with tests using the red-green-refactor loop. Use when implementing any logic, fixing any bug, or changing any behavior. Use when you need to prove that code works, when a bug report arrives, or when you're about to modify existing functionality. Use when asked to add tests to a function, fix a bug in it or change its behavior, even when the code is pasted inline and the request does not mention tests.
Quality judgment
An exceptionally thorough, well-structured TDD skill with concrete code examples, anti-pattern tables, stack-discovery guidance, and explicit trigger conditions including the inline-code edge case. Minor deductions only for TypeScript-only examples and some tangential content (browser DevTools, subagents) that slightly dilutes focus.