TDD Workflow Skill - Test-Driven Development

Purpose

Implement features using strict TDD methodology: write a failing test first, implement the minimum code to pass, then refactor while keeping tests green.

Trigger

User invokes /tdd <requirement description> or orchestrator delegates TDD tasks.

Algorithm

Phase 1: RED (Write Failing Test)

1. ANALYZE the requirement to identify testable behaviors
2. DELEGATE test writing to Tester Expert via Task tool:
   • Write test(s) that define the expected behavior
   • Use existing test patterns/framework found in the project
   • Tests MUST be specific, isolated, and deterministic
3. RUN tests via Bash to confirm they FAIL (this is expected)
4. REPORT RED status with test output

Phase 2: GREEN (Make Tests Pass)

5. DELEGATE implementation to Coder agent via Task tool:
   • Write the MINIMUM code to make the failing test(s) pass
   • No premature optimization or extra features
   • Follow existing code patterns in the project
6. RUN tests via Bash to confirm they PASS
7. REPORT GREEN status with test output
8. If tests still fail, iterate steps 5-7 (max 3 attempts)

Phase 3: REFACTOR (Clean Up)

9. DELEGATE refactoring to Coder agent via Task tool:
   • Remove duplication
   • Improve naming and readability
   • Extract functions if needed (max 30 lines per function)
   • Ensure type hints and docstrings are present
10. RUN tests via Bash to confirm they still PASS
11. REPORT REFACTOR status with test output

Completion

12. PRESENT final summary with all three phases

Output Format at Each Phase

## TDD Cycle: <requirement>

### [RED] Failing Test
- File: <test file path>
- Test: <test function name>
- Result: FAIL (expected)
- Output: <relevant error output>

### [GREEN] Implementation
- File: <implementation file path>
- Changes: <brief description>
- Result: PASS
- Output: <test pass output>

### [REFACTOR] Cleanup
- Changes: <what was refactored>
- Result: PASS (tests still green)
- Output: <test pass output>

Rules

• NEVER skip the RED phase - always start with a failing test
• NEVER write more code than needed to pass the test in GREEN phase
• NEVER refactor if tests are not green
• If tests cannot be run (no test framework), install it first
• Detect test framework from project: pytest, jest, vitest, go test, cargo test, etc.
• Each TDD cycle handles ONE behavior - repeat for multiple behaviors
• Show test output at every phase transition
• If a test is flaky (passes/fails inconsistently), fix the test first

Test Framework Detection

Check in order:

1. pytest.ini / pyproject.toml [tool.pytest] / conftest.py -> pytest
2. jest.config.* / package.json "jest" -> jest
3. vitest.config.* -> vitest
4. Cargo.toml -> cargo test
5. go.mod -> go test
6. Makefile with test target -> make test
7. Fallback: ask user which test command to use