If you are refer to any state testing or standarize testing (sat's p.r.e.p., leap. ex...) Each subject ranges from about 60-90 minutes depending on your grade & state. Questions can be multiple choice, written response, fill in the blank, drag & drop boxes(if the test is done online rather than on computer) as well as finishing graphs & line plots (mathematics & science) and paragraphs or short sentence responses.
Subjects such as Mathematics & Language usally give students around 90 minutes, while Geography,History,Chemistry, Physics,& any similar or relating classes usally give about 60.
If you are stressing about work(i am as well). The best thing to do is study, and get a good nights rest. Try your best & I wish you good luck on any tests that you take. <3