Mockito ArgumentCaptor for Kotlin function

Question

Consider a function that takes an interface implementation as an argument like this:

interface Callback {     fun done() }  class SomeClass {              fun doSomeThing(callback: Callback) {          // do something          callback.done()      }     } 

When I want to test the caller of this function, I can do something like

val captor = ArgumentCaptor.forClass(Callback::class) Mockito.verify(someClass).doSomeThing(captor.capture()) 

To test what the other class does when the callback is invoked, I can then do

captor.value.done() 

Question: How can I do the same if I replace the callback interface with a high order function like

fun doSomeThing(done: () -> Unit) {      // do something      done.invoke()  } 

Can this be done with ArgumentCaptor and what class do I have to use in ArgumentCaptor.forClass(???)

Answer 1

I recommend nhaarman/mockito-kotlin: Using Mockito with Kotlin

It solves this through an inline function with a reified type parameter:

inline fun <reified T : Any> argumentCaptor() = ArgumentCaptor.forClass(T::class.java) 

Source: mockito-kotlin/ArgumentCaptor.kt at a6f860461233ba92c7730dd42b0faf9ba2ce9281 · nhaarman/mockito-kotlin

e.g.:

val captor = argumentCaptor<() -> Unit>() verify(someClass).doSomeThing(captor.capture()) 

or

val captor: () -> Unit = argumentCaptor() verify(someClass).doSomeThing(captor.capture())