Oh, we certainly do massive automated testing. Our release testing script takes currently an 8-core machine about 4 days, and our nightly test runs on about 6 c

Oh, we certainly do massive automated testing. Our release testing script takes currently an 8-core machine about 4 days, and our nightly test runs on about 6 configurations, taking about 2 hours. However, often the units have properties which are very difficult to specify in isolation, and from experience almost all bugs come from many algorithms reading and writing the same data structure (I'm not thinking of threading issues here, although they are another issue). Consider something like a sudoku solver (the things I work on are much more complicated than that). Usually writing the function which checks the condition 'a row/column/box are all different' is very simple. The errors come when these functions interact, each effecting each other as they are called. Certainly, this kind of situation is very unusual. Most people write code which lends itself more naturally to test-driven development, and in those situations I approve of it.