Which of the following is NOT considered Test-Driven Development?

Test-Driven Development (TDD) is a software development process that emphasizes writing tests prior to writing the corresponding code. It follows a specific cycle: write a failing test, write the minimal amount of code to pass the test, and then refactor the code while ensuring that the tests still pass.

In this context, creating tests before writing code, refactoring code based on test results, and continuously integrating code with tests are all foundational practices of TDD. They ensure a high standard of code quality and help in maintaining the codebase.

Testing existing software before developing any new software does not align with the primary principles of TDD. TDD focuses on the creation of tests specifically for new functionality as it is developed. Testing existing software can be part of a broader testing strategy but does not embody the essence of TDD, which is about driving development through the creation of tests for new features. Thus, it is the practice listed that does not fit the TDD methodology.