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tdd-implement

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Implement a feature or fix a bug using strict TDD. Analyzes the requirement, creates tests first, implements minimal code, then refactors. Use for feature requests, bug fixes, or enhancements that need test coverage.

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Source SKILL.md: https://github.com/FastLED/FastLED/blob/HEAD/.claude/skills/tdd-implement/SKILL.md

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TDD Implementation — Feature-Driven Test-First Development

You are implementing a feature or fixing a bug using strict Test-Driven Development. This is a more structured workflow than /tdd — you analyze the requirement, break it into testable behaviors, and implement each one through a full Red-Green-Refactor cycle.

Input

$ARGUMENTS

Step 1: Analyze the Requirement

Actions

  1. Read the requirement carefully — identify what behavior needs to change or be added
  2. Find relevant source code: Use Grep/Glob to locate the files that need to change
  3. Read existing tests: Find any existing test coverage for the affected code
  4. Identify testable behaviors: Break the requirement into 1-5 discrete, testable units

Output

## Requirement Analysis

**Requirement**: [one-line summary]
**Source files**: [list of files that will be modified]
**Existing tests**: [list of related test files, or "none found"]
**Testable behaviors**:
1. [behavior 1 — what it does, how to verify]
2. [behavior 2 — what it does, how to verify]
3. [behavior 3 — if needed]

Step 2: Implement Each Behavior via TDD

For EACH testable behavior, execute a full Red-Green-Refactor cycle:

RED: Write Failing Test

  1. Write a minimal test for this specific behavior
  2. Follow all conventions from agents/tests.md:
    • FL_ prefixed macros (FL_CHECK_EQ, FL_REQUIRE_TRUE, etc.)
    • Include test.h and FastLED.h
    • using namespace fl; + anonymous namespace
    • Mirror source path for test file placement
  3. Run bash test TestName — verify it FAILS for the right reason

GREEN: Minimal Implementation

  1. Write the minimum code to make this test pass
  2. Do NOT implement other behaviors yet
  3. Run bash test TestName — verify it PASSES
  4. Run bash test --cpp — verify no regressions

REFACTOR: Clean Up

  1. Improve code quality without changing behavior
  2. Run tests after each change to verify they stay green

Report Each Cycle

### Behavior N: [description]
- RED: Test written at tests/fl/foo.cpp — FAILS (expected: [reason])
- GREEN: Implemented in src/fl/foo.h — PASSES
- REFACTOR: [changes made, or "clean as-is"]

Step 3: Integration Verification

After all behaviors are implemented:

  1. Run full test suite: bash test --cpp
  2. Check for regressions: Verify ALL tests pass, not just new ones
  3. Review changes holistically: Ensure the implementation is cohesive
  4. Run code review: Check changes against FastLED coding standards

Output

## Integration Verification

**Full test suite**: [X/X] tests pass
**New tests added**: [count]
**Source files modified**: [list]
**Regressions**: None / [details if any]

Step 4: Final Summary

## TDD Implementation Complete

**Requirement**: [what was implemented]
**Approach**: [brief description of the solution]

### Files Changed
| File | Change Type | Description |
|------|-------------|-------------|
| tests/fl/foo.cpp | Added | 3 test cases for [feature] |
| src/fl/foo.h | Modified | Added [function/method] |

### Test Coverage
- [Test case 1]: [what it verifies]
- [Test case 2]: [what it verifies]
- [Test case 3]: [what it verifies]

### All Tests Passing: Yes

Key Rules

  • Test FIRST, implement SECOND — this order is absolute
  • One behavior per cycle — don't batch multiple behaviors
  • Minimal implementation — write the simplest code that passes
  • Run tests at EVERY transition — RED->GREEN->REFACTOR each verified
  • Stay in project root — never cd to subdirectories
  • Use bash test wrapper — never bare python, meson, or ninja
  • Extend existing test files — don't create new ones unless necessary
  • No mocks — use real objects and values