I first had the language interview (my interview was in Colombia, we speak spanish here so I had to demonstrate I had the required level on english for the position as they send people to the US for the trainning). After you pass that english test you have the psychological test with HR. After those two tests you go to the interview with the engineer that is going to be in charge of you (your boss) and he/she is the one who decides if you are going to be selected or not. If you pass that then you have the medical exam to prove you don´t have any problems the company will have to pay in the future. After all that you just need to sign your contract and start working there