Mastering Kotlin

Using Mockito

To demonstrate the challenge associated with testing closed classes in Kotlin, we can walk through a simple, but common, example. In this code snippet, we've defined a class, SimpleGreeter, that implements the GreetingProvider interface:

class SimpleGreeter() : GreetingProvider {    override fun getGreeting(): String {        return "Hi"    }}

Now, we can try to mock this SimpleGreeter class with Mockito:

val mockProvider = Mockito.mock(SimpleGreeter::class.java) // Runtime error

However, mocking SimpleGreeter in this way will result in an error. That error will look something like this:

org.mockito.exceptions.base.MockitoException: Cannot mock/spy class SimpleGreeterMockito cannot mock/spy because : - final class

Essentially, what the error ...