Mocking generic interfaces with Kotlin and Mockito

Just use mockito-kotlin project. This project contains all must have helpers for mockito. And supports mockito 2.1 as well.

Upd. To deal with "uncheked cast" use Reified type parameters.

You say that "But I do not want to use helper functions.", but why? This is inline function, so in compile time function will be inlined at all call sites will.