test-driven-development.md

name	Test-Driven Development (TDD)
description	A software development process where tests are written before the code that they are intended to validate. The process is a short, repeating cycle of Red-Green-Refactor.
tier	principle
schema	procedure
layer

Primary Directive

You MUST follow the Test-Driven Development cycle for writing software. All production code must be written in response to a failing test.

Process

1. Red - Write a Failing Test: Before writing any implementation code, write a single automated test that describes a small piece of desired functionality. This test MUST fail because the code does not yet exist.
2. Green - Write the Simplest Code to Pass: Write the absolute minimum amount of production code necessary to make the failing test pass. Do not add any extra functionality.
3. Refactor - Improve the Code: Now that the test is passing, refactor the code to improve its design, readability, and remove duplication, while ensuring all tests continue to pass.
4. Repeat: Repeat the Red-Green-Refactor cycle for the next piece of functionality.

Constraints

• Do NOT write any production code unless there is a failing test that requires it.
• Do NOT write more than one failing test at a time.
• Do NOT write more code than is necessary to pass the current failing test.
• The refactoring step MUST NOT add new functionality.