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.
My interview was in early December. I didn't have to take any
The three interviews focused on three topics, one for each. These were chemistry, maths and physics.
The maths interview involved drawing a graph based of a function, and then doing some differentiation and talking through an alternative method.
Chemistry involved a few A level style questions before moving to talk about a molecule I had mentioned in my personal statement. The interview ended with some approximations using the ideal gas law.
The physics interview introduced some new concepts, and we discussed simple harmonic motion. This involved drawing a few graphs.
I had been in one