In Test-Driven Development (TDD), what is the purpose of writing multiple tests for a single unit of code (method or class) in Java?To ensure that the code is as short as possible.To achieve 100% test coverage for that unit of code.To validate different scenarios and cases.To reduce the time required for test execution.

The purpose of writing multiple tests for a single unit of code (method or class) in Java in Test-Driven Development (TDD) is to validate different scenarios and cases.

Here's a step-by-step explanation:

1. Understand the Requirement: The first step in TDD is to understand the requirement or functionality that the code needs to implement.

2. Write a Test: Once the requirement is clear, you write a test that checks whether the code meets this requirement. This test will fail initially because the code it's testing doesn't exist yet.

3. Write the Code: Now, you write the minimum amount of code needed to pass the test. This ensures that you're only writing code that's necessary for the functionality you're working on.

4. Run the Test: After the code is written, you run the test. If it passes, you know that your code meets the requirement. If it fails, you need to update your code and test again.

5. Refactor: Once the test passes, you can refactor your code to improve its structure or efficiency while maintaining its behavior. The test ensures that this refactoring doesn't break the code.

6. Write More Tests: Now, you write more tests for the same unit of code to check different scenarios and cases. For example, if you're testing a method that calculates the square root of a number, you might write tests for positive numbers, negative numbers, and zero. Each of these tests represents a different scenario that the code needs to handle correctly.

By writing multiple tests, you ensure that your code works correctly in all these different scenarios. This helps to catch any bugs or issues early in the development process, making them easier and cheaper to fix.