What is TDD (Test-Driven Development)?

TDD (Test-Driven Development) is a software development methodology where tests are written before the actual code that needs to pass these tests.

The TDD process follows the "Red-Green-Refactor" cycle:

1. Red: A small test case is written for new functionality. This test should initially fail because there is no code to satisfy it.
2. Green: The minimal necessary code is written to pass the test. The goal at this stage is simply to make the test pass, without regard to perfect architecture or design.
3. Refactor: After the tests pass, the existing code (both test and production code) is refactored to improve its structure, readability, and efficiency, while ensuring all tests continue to pass.

Advantages of TDD:

• Improved code design: Tests encourage thinking about interfaces and code dependencies.
• Reduced errors: Bugs are detected early in the development process.
• Confidence in code: A comprehensive set of tests allows safe refactoring and addition of new features.
• Improved documentation: Tests serve as examples of how to use the code.
• Increased productivity: Less time is spent debugging at the end of the development cycle.

TDD does not replace other types of testing but serves as a powerful tool to improve the development process and code quality at the modular level.