One 90 minutes exam. It was to be followed by face-to-face interviews. As noted by others here, the exam is lengthy and I failed. From there they walked me to the door.
Even though I failed, I'm rating the exam average difficulty because the concepts needed are very very basic. But you have to be able to do many calculations without mistakes from beginning to the end, and quickly.
I'm also rating the overall experience negative only because being my first interview ever I expected that at least gain experience with face to face interviews, but unfortunately I didn't even get that far.