What is the primary advantage of test-driven development (TDD)?

The primary advantage of test-driven development (TDD) is that it enhances code quality. TDD is an approach where tests are written before the actual code implementation. This process encourages developers to think through the requirements and design of the code before writing it, which often results in clearer, more efficient, and well-structured code.

By focusing on writing tests first, developers are motivated to create only the necessary code to pass those tests, which can lead to less complex and more modular designs. Additionally, as changes or new features are added, the existing tests provide immediate feedback, helping to ensure that previously functioning code remains intact. This iterative cycle of writing tests, coding, and refactoring significantly contributes to a higher overall quality of the software.

In contrast, while options related to project costs or documentation needs may reflect other considerations within software development, they don't capture the definitive advantage of TDD in enhancing the quality of the code itself. Speeding up coding processes may occur as a secondary benefit, but the main strength of TDD lies in its focus on improving code integrity and maintainability.