Quote Originally Posted by phantomotap View Post
For most code you'll never prove that it is correct... only that it seems to behave correctly.
True, but testing is not about correctness proving, it is about checking to see if something seems to behave correctly .

Also worth noting: proving something correct does not actually mean it will then seem to behave correctly, if you have misconceived the application of what you have proven correct.

I don't test what I write as much as I should (because I enjoy debugging later so much) but I did read somewhere that "studies have shown" that the number of bugs found in say 10 poorly tested units over the next 6 months will be much higher than those found in 10 similar but well tested units, even if the exact same people wrote all the code -- regardless of whether anything is "proven correct" in the process.