Mockito for Kotlin

This wiki contains brainstorming and plan to provide first class support for Kotlin language. Mockito currently works with Kotlin, but the syntax is not optimal.

Ideas and challenges

• Kotlin has very nice lambda support which creates opportunities to improve Mockito API.
• In Kotlin, all classes are final by default. Mockito cannot mock final class by default (#657).
• Kotlin support can be similar (same?) as Java8 support. Currently, Mockito supports Java8 lambdas via separate GitHub project maintained by Marcin Zajączkowski.
• There is an existing mockito-kotlin library, maintained by Niek Haarman, see the GitHub project.

Brainstorming

//mock creation
val mock = mock<MyClass> {
    when { getText() } thenReturn "text"
    given { getText() } willReturn "text"
}
val mock = mock<MyClass>(withSettings().stubOnly()) {
    //...
}

//stubbing / expecting
given(mock.foo(argThat { x < 100 })).willReturn("x")

//verification
verify {
  mock.foo(any())
  mock.bar()
  mock.baz(argThat { x > 100 })
}