What is the practice of writing a failing test first, then writing the code that causes the test to pass, then refactoring the code to make it cleaner?

The practice of writing a failing test first, then writing the code that causes the test to pass, then refactoring the code to make it cleaner is known as Test-Driven Development (TDD).

Here are the steps involved in TDD:

1. Write a test: In this step, you write a test for the functionality you want to implement. This test is supposed to fail because you haven't written the implementation code yet.

2. Run the test: You run the test to ensure it fails. This might seem counter-intuitive, but it's an important step to confirm that the test is not falsely positive and it's indeed testing what it's supposed to test.

3. Write the code: Now, you write the minimum amount of code that will make the test pass. This means you focus only on the functionality that you're currently testing.

4. Run the tests: You run the tests again. If the tests pass, you move on to the next step. If they don't, you need to update your code and try again.

5. Refactor the code: Once the tests pass, you can refactor your code to improve its structure or efficiency while keeping the functionality intact. The key here is to make sure that the changes don't cause the tests to fail.

6. Repeat: You repeat these steps for every new functionality you want to implement.

This practice is widely used in software development to ensure the code is error-free and meets the requirements. It also makes it easier to maintain and extend the code in the future.