Writing a test suite so comprehensive that the only programs that satisfy it are correct wrt the specification amounts to writing a formal proof, which is in most cases orders of magnitude harder and more time consuming than writing the code yourself.

Programming is ironically one of the worst use cases of AI, because often predictable failure is better than unexpected success.

"Fix the null pointer exception" is less expensive (time, money and mental energy) than "figure out why the code spits out garbage even though the test cases pass".

This will take approximately eternity for difficult problems, such as management changing their mind every day.