Too Long; Didn't Read
With Kotlin in place, in order to support Mocking Kotlin class without opening it, we would require Mockito 2.0. Check out <a href="https://android.jlelse.eu/fixing-unit-test-issue-of-rxjava-chain-and-kotlin-746fcef5ade8">my blog</a> on the detail. In migrating from Mockito 1 to Mockito 2, faced two issues that need some exploration before one could solve it. Hence shared it here.