Test-Driven Development (TDD) is a software development approach that emphasizes writing automated tests for code before actually writing the code itself. TDD involves writing a test case that specifies the behavior of the code to be developed, running the test, and then writing the minimum amount of code required to pass the test. The process is then repeated for each new feature or modification to the codebase.

The TDD approach has several benefits. By writing tests before writing code, developers are forced to think carefully about the requirements and expected behavior of the code. This can help to catch potential bugs and edge cases early in the development process, reducing the cost of fixing them later on. TDD also helps to ensure that the code is modular, reusable, and maintainable, since each new feature is developed in isolation and must pass a set of tests before it can be integrated into the main codebase.

The TDD approach consists of three stages:

1. Write a test case: The first step in TDD is to write a test case that specifies the behavior of the code to be developed. The test case should be written in a way that can be automated, and it should be clear and unambiguous.

2. Run the test: After writing the test case, the developer runs the test to ensure that it fails. This step is important because it ensures that the test is actually testing what it is supposed to test.

3. Write the minimum amount of code required to pass the test: The next step is to write the minimum amount of code required to pass the test. This code should be simple, clear, and focused on passing the test.

The process is then repeated for each new feature or modification to the codebase.

The TDD approach is often used in combination with other software development practices, such as Agile development and Continuous Integration/Continuous Deployment (CI/CD). TDD helps to ensure that code is thoroughly tested and ready for integration into the main codebase, making it a valuable tool for any software development project.