Testing interactions between smart contracts How?

I've looked at the tests in the open zeppelin repository and some tutorials and got a pretty good understanding of unit test and wrote some of my own for a sample smart contract.

I'm trying to understand integration testing though i.e. testing interactions between smart contracts.

Are there any integration tests in the open zeppelin repository that I can look at? I did a bit of searching on my own and couldn't find any. If not, would anybody please suggest some repos that contain integration tests for smart contracts? I'm looking to understand how integration tests are written

Also any guidance on how to go about testing interactions between smart contracts is greatly appreciated!

Please do not ask the same question, I will close this topic and just keep a valid one.