Fifteen Rules for Test‑Driven Development (TDD)

Test‑Driven Development (TDD) can feel easy or hard depending on one’s mindset; the following fifteen actionable rules, sourced from the book “The Craftsman’s Clean Code: Professionalism for Programmers,” provide clear guidance for disciplined TDD practice.

Write tests first; they force you to clarify the code you intend to write.

Let tests fail, then pass, and clean up the code.

Avoid digging for “gold” (hard or interesting puzzles) prematurely.

Start with the simplest, most specific, and easiest‑to‑fail test.

Generalize when possible.

If the code feels wrong, fix the design before proceeding.

Exhaust simple case testing before moving to a more complex test.

If many implementation lines are needed to pass a test, discard that test and write a simpler one.

Proceed calmly and incrementally through all tests.

Do not add unnecessary things to tests.

Avoid using production data in tests.

Decouple test structure from production code structure.

The more specific the test, the more generic the code becomes after refactoring.

If a transformation yields an unsatisfactory solution, try a different transformation.

Avoid using a debugger whenever possible.

The core discipline of TDD consists of two simple points: short cycles (minutes or even seconds) and writing tests first.

Refactoring and TDD are twin brothers; both are indispensable for maintaining clean, maintainable code.