tdd
Use when writing production code that needs tests - new features, bug fixes, refactoring. Enforces RED-GREEN-REFACTOR cycle before any implementation.
What this skill does
# TDD Skill Write the test first. Watch it fail. Write minimal code to pass. ## The Iron Law **No production code without a failing test first.** Every line of production code must be justified by a test that failed without it. No exceptions. No shortcuts. No "I'll test after." --- ## Agent Workflow ``` 1. DETECT -> Identify stack, test framework, existing test patterns 2. RED -> Write ONE failing test for the next behavior 3. VERIFY -> Run test, confirm it fails for the EXPECTED reason 4. GREEN -> Write the SIMPLEST code that makes the test pass 5. VERIFY -> Run tests, confirm ALL pass (new + existing) 6. REFACTOR -> Clean up while keeping all tests green 7. REPEAT -> Next behavior = next failing test ``` **CRITICAL**: Never skip VERIFY steps. A test that passes on first run proves nothing. --- ## RED-GREEN-REFACTOR Cycle See [references/red-green-refactor.md](references/red-green-refactor.md) for the detailed cycle with rules and verification steps. --- ## Reference Guide | Topic | Reference | |-------|-----------| | Full RED-GREEN-REFACTOR cycle | [red-green-refactor.md](references/red-green-refactor.md) | | Common mistakes and red flags | [anti-patterns.md](references/anti-patterns.md) | | Per-stack test commands | [stack-commands.md](references/stack-commands.md) | --- ## Quick Reference: Test Commands | Stack | Run Tests | Watch Mode | |-------|-----------|------------| | React/Next.js | `npx vitest run` | `npx vitest` | | Laravel | `php artisan test` | `php artisan test --watch` | | Swift | `swift test` | - | | Generic TS | `bunx vitest run` | `bunx vitest` | | Go | `go test ./...` | - | | Rust | `cargo test` | `cargo watch -x test` | --- ## Forbidden Behaviors - Never write production code before a failing test - Never skip the VERIFY RED step - Never accept a test that passes on first run without investigation - Never mock what you can test directly - Never write more than one test at a time in RED phase - Never add features beyond what the current test requires
Related in Writing & Docs
jax-development
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nature-article-writer
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deckrd
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clinical-decision-support
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handling-sf-data
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accelint-ac-to-playwright
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