Language-Agnostic Testing Principles

Test-Driven Development (TDD)

The RED-GREEN-REFACTOR Cycle

Use this cycle for new or changed executable behavior and reproducible bug fixes. For a behavior-preserving refactor, first confirm existing tests pass or add passing characterization tests, then refactor and rerun the same regression evidence.

1. RED: Write a failing test first

   • Write the test before implementation
   • Ensure the test fails for the right reason
   • Verify test can actually fail

2. GREEN: Write minimal code to pass

   • Implement just enough to make the test pass
   • Focus on making it work