Interview 1: justifying events that are considered 'bad', logic; Interview 2: A-Level maths questions, game theory, and patterns
Watched mock interviews online, and introductory philosophy videos
Past Papers, Jesus College videos
They want you to demonstrate that you can answer a question that you don't know the answer to by asking them for relevant help
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: Thinking Skills Assessment
Number of interviews: 2
Time between interviews: (how-long-were-you-waiting-between-your-interviews)
Length of interviews: (how-long-were-each-of-your-interviews)
Online interview: (were-your-interviews-conducted-online)
I had two interviews for PPE: Politics and Philosophy in one, and Economics in the other, and each had two tutors in them (one for each subject). Politics focused on justifying events that are considered 'bad', and then the philosophy around logic and justifying true and false statements using previously established facts/ statements. Economics started with A-Level maths questions, and then progressed to questions relating to game theory and patterns.
The most useful thing I did to prepare for my interviews was watch some practice interviews for my subject (and other related subjects) on various Oxford University YouTube channels (it makes them seem a lot less daunting!). Additionally, coming from a state school, we didn't have any specific tutorial prep advice from our teachers, however, one of my friends was applying for a similar subject at Cambridge, so we googled practice questions, and took turns asking and answering them with each other in free periods. Something that massively helped me was watching introductions to the subject on YouTube in the week before my interview (in my case I was applying for PPE, but only really knew about Economics as I had studied it at A-Level, therefore I watched an Introduction to Philosophy which came in infinitely useful, as although in some subjects you aren't technically required to have any prior knowledge, it helps with nerves and understanding the questions they are asking, along with giving you a basis for starting your reasoning and answers!)
I tried the past papers and watched some videos by Matthew Williams on the Jesus College Oxford YouTube account
Try to learn the basics of your subject you are applying for, and then treat the interview as more of a conversation rather than a test. They don't want you to demonstrate that you know the answers, they want you to demonstrate that you can answer a question that you don't know the answer to by asking them for relevant help, and trying to reason and infer your way around with your current knowledge