Add, update, or repair tests for behavior, regressions, and test-first development. Use when the user asks for tests, TDD, red-green-refactor, regression coverage, test repair, or behavior-driven implementation.
Installation
Install with Codex or Claude Copy this prompt, paste it into Codex, Claude, or another assistant, and let it review the skill page and install it for you.
Add, update, or repair tests for behavior, regressions, and test-first development. Use when the user asks for tests, TDD, red-green-refactor, regression coverage, test repair, or behavior-driven implementation.
Test
Input
A behavior, bug, module, feature, failing test, or uncovered path to test.
Use explicit input first; otherwise infer from context, recent edits, selected files, or branch.
Safest default: identify public behavior and highest-risk paths before writing tests.
Workflow
Define behavior. Identify the public interface and the behavior that matters to the user.
Pick the first slice. Choose one narrow behavior that proves the path end to end.
Write or repair tests. Prefer behavior-facing tests over implementation-detail tests.
Use TDD when requested. Red: write one failing test. Green: write the smallest implementation that passes. Repeat by slice.
Refactor when green. Simplify duplication, names, and module shape after tests pass.
Validate. Run relevant tests, typecheck, lint, or build commands.
Output
Behaviors covered
Tests added, changed, or repaired
Implementation changed, if any
Validation run
Remaining test gaps
Guardrails
Do not write all tests before all implementation when using TDD.
Prefer tests through public interfaces over private functions and internal mocks.
