As said above, the MGMAT tests give you an excellent post-test breakdown with as much info as you would hope for.

One point I’d like to make is that you will never have as much time as you want an an adaptive test like the GMAT. This is because when you get a question right, you'll get a harder question next. Eventually, if you are doing well, you will get questions that are past the difficulty that you can comfortably handle in 2 – 3 minutes. If you try to do many of these, you’re going to run out of time in the end.

When I get any question that looks like it’s beyond my ability to do in 2 – 3 minutes, I resort to effective guessing. If you can eliminate 2 or 3 of the possible answers and then make an educated guess, you have a fair shot at getting it correct. More importantly, if you can do this in under a minute, then you’ll have more time to devote to the problems you really know.