Why would you test implementation details? Test what's delivered, not how it's delivered. The thinking portion, synthetized or not, is merely implementation.
The resulting artefact, that's what is worth testing.
Because this has never been sufficient. From things like various hard to test cases to things like readability and long term maintenance. Reading and understanding the code is more efficient and necessary for any code worth keeping around.
The resulting artefact, that's what is worth testing.