Test Driven Development

Test-Driven Development

Classic TDD workflow: write a failing test first, make it pass with minimal code, then refactor. Enforces discipline and produces well-tested, clean code.

When to Use

• Starting a new feature or module
• Fixing a bug (write a test that fails first)
• Refactoring existing code
• Any time you want confidence in your code

Procedure

RED Phase

1. Write a test for the next small behavior
2. Run the test, confirm it fails
3. Check the error message makes sense

GREEN Phase

1. Write the simplest code that makes the test pass
2. Run the test, confirm it passes
3. Do not add anything the test does not require

REFACTOR Phase

1. Improve the code while keeping tests green
2. Remove duplication
3. Clarify naming
4. Run tests again to confirm nothing broke

Cycle

Repeat RED-GREEN-REFACTOR in small increments. Each cycle should take 2-10 minutes. If it takes longer, the step is too big.

Pitfalls

• Writing multiple tests before making any pass
• Skipping the refactor phase
• Writing tests after the code
• Making the Green phase too elaborate

Verification

• All tests pass
• Each test covers one specific behavior
• Code is free of duplication
• You can delete any test and see it fail

How to use?

1. Download

Go to the AGENT KD SKILL gallery and find this skill card. Click Download to save the SKILL.md file.

2. Install

Copy the downloaded SKILL.md into your agent's skills directory:

3. Use

Restart your agent session. The skill will auto-load when implementing features.

4. Verify

Ask your agent to implement something using TDD. If it writes tests first, you're all set.