GIAC Practice tests

in GIAC
How close are the practice tests to the actual exam? I know the format is dead on, but material wise are the questions similar in regards to detail, topics, etc? I've seen some practice tests that are designed to measure your knowledge, but the actual material and question formatting are completely different.
If I'm passing the practice exams closed book without any issues, can I assume that I'm ready for the actual test?
If I'm passing the practice exams closed book without any issues, can I assume that I'm ready for the actual test?
Comments
How I use my practice tests are to validate my index and use time management techniques, as the time limit and number of questions are the same on practice test and actual exam. if I can finish my practice test within time and easily find most items in my Index then I am confident I can replicate this on the actual test. If I notice I am running out of time then it tells me I need to put more studying in.
Hope this helps.