To prove the correctness of your code you would write tests in similar way as SQLite does, no? They have, like, 100x more lines of code for tests than actual code they test?
There could always be another rare edge case.
Imagine trying to unit test all possible cases of Pythagorean theorem being correct vs a single proof in a few lines of descriptive logic.
"Program testing can be used to show the presence of bugs, but never to show their absence!"
Dijkstra (1970)