Remember this advice isn't official. There is no guarantee it will reflect your experience because university applications can change between years. Check the official Cambridge and Oxford websites for more accurate information on this year's application format and the required tests.
Also, someone else's experience may not reflect your own. Most interviews are more like conversations than tests and like, any conversation, they are quite interactive.
Test taken: Economics Admissions Assessment (ECAA)
Number of interviews: 3
Skype interview: No
Time between interviews: A few hours
Length of first interview: 15-30 minutes; Length of second interview: 15-30 minutes; Length of third interview: 15-30 minutes
I had a tutor interview (which was based on my personal statement), and then two subject interviews. My second interview was very chill and it was more like a chat. My third interview was more intimidating. I had a sheet of questions to answer before I went in, and I then had to answer them in front of the interviewer.
Past papers and