testDriven

Test-driven development (TDD) is a software development practice that emphasizes writing automated tests before implementing the corresponding functionality. The core idea is to define the desired behavior of a small unit or feature through tests that initially fail, then implement just enough code to satisfy the tests, and finally refactor the code while keeping all tests green.

Typical workflow is red-green-refactor: write a failing test (red), write code to pass it (green), then refactor for clarity and maintainability without changing external behavior.

Tests are usually unit tests, but acceptance and integration tests can be included. TDD encourages modular, loosely coupled design and can guide API surface and class responsibilities by forcing small, testable units.

History: Kent Beck introduced TDD within the XP framework in the late 1990s; it gained mainstream attention after the publication of Test-Driven Development by Example (2003).

Benefits: provides a safety net for refactoring, improves code quality, documents intended behavior, and can reduce debugging time. It can also lead to better test coverage and design.

Criticisms and limitations: if tests are closely tied to implementation, refactors can break tests; initial pace may be slower; not all projects benefit equally; maintaining tests requires discipline; over-reliance on unit tests may miss integration issues; tests must be well designed and independent.

Adoption: common in Agile and DevOps environments; supported by unit testing frameworks (JUnit, NUnit, pytest, etc.) and continuous integration pipelines; can be complemented by behavior-driven development (BDD) and property-based testing.