TDD in Agile: Building Quality from the First Line of Code
In agile development, Test-Driven Development (TDD) ensures high-quality, reliable code. As Robert C. Martin (Uncle Bob) says, “As the tests get more specific, the code gets more generic.” This means that as tests narrow in on details, the code becomes more flexible and adaptable.
TDD follows extreme programming (XP) principles, where the product is only ready once it passes all required tests. This process involves writing unit tests before actual code, ensuring each feature behaves as expected.
The TDD Circle of life :
As Uncle Bob defines three laws:
Law 1: You are not allowed to write any production code unless it is to make a failing unit test pass — Only write production code to make a failing test pass.
Law 2: You are not allowed to write any more of a unit test than is sufficient to fail; and compilation failures are failures — Write just enough of a test to make it fail (even if it doesn’t compile).
Law 3: You are not allowed to write any more production code than is sufficient to pass the one failing unit test — Write only enough code to pass the test, avoiding unnecessary functionality.
This approach is slightly different from traditional Scrum. In TDD, tests drive development by guiding what needs to be built. Unit tests define the behavior of different user personas, resulting in verifiable code outcomes.
TDD is a practice, is a skill and it is a way of working
In TDD — Definition of Done becomes not just code(verifiable) but also automated Test Cases.
However this doesn’t mean we need less QA. Rather TDD fits in the Test Pyramid, by fastening the software delivery with lot of contextual automation test cases — which can save lot resources(time and money) to software.
Let’s understand few queries :
Myth : Having TDD slows down the Development time? 👆
Reality: TDD actually speeds up quality delivery in agile teams. By following Uncle Bob’s Law 1 — writing tests first — you ensure a deep understanding of requirements from the start. Writing unit tests early encourages discussions and validations with clients or stakeholders before coding begins, reducing back-and-forth with QA. The result? Faster releases, with fewer bugs, and higher-quality code.
Jumping straight into coding is rarely an effective way to approach problem-solving.
Development time = release software + time it takes to fix bug to release software
How to get started with TDD(kata)? 👆
In martial arts, kata are drills that build muscle memory. Similarly, TDD katas are coding exercises that help you practice the fundamentals of TDD. Start with simple TDD katas here to build a solid foundation.
