What is a test-driven development (TDD) cycle and what are its phases?

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What is a test-driven development (TDD) cycle and what are its phases?

Test-driven development (TDD) is a software development approach that emphasizes writing tests before writing the actual code. It follows a cycle consisting of several phases to ensure the development process is systematic and efficient. The phases of the TDD cycle are as follows:

1. Write a failing test: In this phase, the developer writes a test case that checks for a specific functionality or behavior that is currently missing in the code. The test is intentionally designed to fail since the corresponding code has not been implemented yet.

2. Run the test: The failing test is executed to validate that it indeed fails as expected. This step ensures that the test is correctly written and that the test environment is properly set up.

3. Write the minimum code: In this phase, the developer writes the minimum amount of code required to pass the failing test. The focus is on implementing the necessary functionality without adding any unnecessary complexity.

4. Run all tests: After writing the code, all the previously written tests, including the failing test, are executed. This step ensures that the newly implemented code does not break any existing functionality.

5. Refactor the code: In this phase, the developer improves the code's design and structure without changing its functionality. The goal is to enhance the code's readability, maintainability, and performance.

6. Repeat the cycle: The TDD cycle is repeated for each new functionality or behavior that needs to be implemented. The process starts again by writing a failing test for the next requirement, followed by writing the minimum code, running all tests, and refactoring the code.

By following the TDD cycle, developers can ensure that their code is thoroughly tested, maintainable, and meets the desired requirements. It promotes a more reliable and efficient development process by catching bugs early and providing a safety net for future changes.