Hi, Rakell, I've never taken any of these tests, nor am I familiar with their directives about the "proper" use of contractions, so I don't know the answer to your question. But I took a quick look at TOEFL's own use of them in this TOEFL Planner document, and ran across the following:
"You’ve been studying English for some time now, so you’ve developed a level of proficiency in your reading, listening, speaking and writing skills. Now you’ll want to make sure you’re familiar with the test format and that you’re ready to do your best. This Planner gives you test information, sample questions and activities to build your skills, and much more." (p. 6) From http://www.ets.org/s/toefl/pdf/toefl_st ... lanner.pdf
Wow. Does TOEFL really advise against the use of contractions in formal writing?