Some things I'd like to see integrated into a RAD programming unit test framework (ie. JUnit) for doing XP:

1. Automatic unit tests.

For example, if one or more (in) parameters passed to a function is null, what does the function do? This check should be automatic in unit testing and should not have to be written explicitly save for the result. If a test isn't written at all, the unit tester should complain.

2. Tests for specific defects.

A defect is opened. To close it, you need to write a test that replicates the defect and make sure it fails with the current code. Then you change (refactor/repair) the program code until it passes. Now you have a regression test for this defect and if the test fails you know the defect is back.

3. Built-in code coverage analysis

If you are truly doing test-driven development, at any given time all lines in the program code should be executed by all tests. If this is not true, develop tests to exercise these lines or, even better, get rid of the superfluous lines.

4. A user-interface library that supports verification.

How can I be sure that the user interface is correct at any given time without manually verifying it? The UI library should be written so that any element in the UI can be programmatically checked for properties such as visibility, position, etc. To see how involved this task can be, check out Liar Views.

5. User-interface can be controlled programmatically

Any defect replicated in the field must be able to be replicated programmatically for a unit test.