Test taken: History Aptitude Test (HAT)
Number of interviews: 3
Time between interviews: A few hours up to an entire day.
Length of interviews: 20-30 minutes, roughly.
Online interview: No

I had three interviews (two with my interviewing College and one with the College that accepted me) - the broad concepts of them were more-or-less the same: assessment of knowledge, interest, and then capabilities in things like source analysis, interpretation of sources, etc. It was set up so I had an entire interview wherein we discussed the essay I submitted (I'll admit; I didn't want to talk about it, it was a little old, and I didn't care for the subject anymore) and a following interview wherein I was given a source and told to analyse it. Both were roughly half an hour in length, and less worrying than I thought they'd be. My third interview ( with the College that accepted me) was shorter and contained a mix of the previous two topics, though we discussed my interests as listed on my personal statement rather than the essay I submitted, which I preferred. Each interview had two professors, and occasionally someone else (I forgot the title, sorry lol) sitting in. It's a bit stressful at the start, but settling in isn't so difficult once you get a grasp of what you're doing.

I did a few practice interviews with my IB Co-ordinator, and went over what exactly to expect from the interviews with her as well. Honestly, I thought it was really good preparation but it ended up being a lot more complicated than the actual interviews were - so, good preparation I guess. Definitely recommend finding someone to practice with, and figuring out the format of your interviews beforehand (however this is often not possible, so don't worry).

I didn't do much honestly - looked up the format of the test, decided it looked like an IB History Paper 1, and decided to wing it.

If you have stuff you submitted (essays, personal statements, etc.) review them before the interview. You will not remember what the essay you wrote in July and handed over in mid-October will contain by the time your interview rolls around! Re-read it, so you understand the gist of it, at the least! As for tests - the HAT is very much not a test of material knowledge but of your ability to interpret information. Practice that, but don't go around attempting to predict the subject of the test and suddenly become a mastermind know-it-all in the subject - you will not be able to. And please, make sure you read all/some of the test papers. Someone in my application pool didn't and failed the test as a result.