In the end you'll always have to manually validate the output, to ensure that what the test case tests is correct. When you write a test case, that's always what you need to do, to ensure that the test case passes in the right conditions, and you have to test that manually.

Since you have to test that manually anyway, you can have AI write the code first; you test it; if it's the right result, you tell AI this is correct, so write test cases for this result.