tdd

name	tdd
description	Use when the user asks for test-first work, red-green-refactor, a TDD fix plan, or behavior-focused tests.

TDD

Use a vertical red-green-refactor loop.

Workflow:

• Identify the public interface or user-visible behavior first.
• Write one failing test for one behavior.
• Implement the smallest change that makes it pass.
• Repeat with the next behavior.
• Refactor only while tests are green.

Test rules:

• Test observable behavior, not private implementation.
• Prefer public APIs, command output, UI state, or persisted effects.
• Mock only system boundaries: external services, time, randomness, filesystem, or network.
• Avoid mocking internal modules you control.

Avoid:

• Writing all tests before implementation.
• Testing data shape that is not part of the contract.
• Adding speculative behavior for future tests.