Sorting is one of the more favorable tasks for being specified this way, for much code there is no simpler way to verify the output than running the same or equ

Sorting is one of the more favorable tasks for being specified this way, for much code there is no simpler way to verify the output than running the same or equivalent code again. If your specification language is not Turing complete then there is simply stuff you cannot specify. Of course, just because it isn't Turing complete doesn't mean it isn't perfectly adequate for writing bugs.