Do you have any particular problems with it?

I just don't know how's the proper way to make it work

What do you mean? With mocking?

i’m using jmockit (not mockito). most of the problems revolve around the fact that jmockit doesn’t actually support kotlin. if the kotlin compiler generates byte code that is different from the java one, things often break. so far i’ve been able to work around things by looking at the byte code, decompiling it, and mocking the java version. this is particularly a problem when you use things like companion objects, default interface implementations, etc.