Test-driven development (TDD) is a software development process that emphasizes writing tests before developing the corresponding code, fundamentally transforming traditional testing methodologies. Unlike the linear waterfall model, TDD integrates testing into a continuous, iterative cycle of writing a test, coding to pass the test, and refactoring. This approach aligns with Agile principles, enhancing collaboration and ensuring that development is closely tied to user expectations and business objectives. TDD encourages a quick feedback loop, improving code quality and reducing long-term maintenance costs by detecting bugs early in the process. It also complements continuous integration/continuous delivery (CI/CD) practices by ensuring a comprehensive suite of tests supports new features, thus enabling rapid and reliable software releases. Best practices for implementing TDD include simplifying tests, using expressive assertions, organizing tests effectively, and maintaining a comprehensive test suite, all of which contribute to creating an efficient and maintainable codebase.