mockito-kotlin

Analytics.kt

interface Analytics<in T> {
    fun send(event : T)
}

Event.kt

data class Event(val foo: String)

SomeTest.kt

import com.nhaarman.mockito_kotlin.KArgumentCaptor
import com.nhaarman.mockito_kotlin.argumentCaptor
import org.assertj.core.api.Assertions.assertThat
import org.junit.Before
import org.junit.Test
import org.mockito.Mock
import org.mockito.Mockito.verify
import org.mockito.MockitoAnnotations

class SomeTest {

    @Mock
    private lateinit var analytics : Analytics<Event>

    private val captor : KArgumentCaptor<Event> = argumentCaptor()

    @Before
    fun setup() {
        MockitoAnnotations.initMocks(this)
    }

    @Test
    fun foo() {
        val event = Event("foo")
        analytics.send(event)
        verify(analytics).send(captor.capture())

        assertThat(captor.firstValue).isEqualTo(event)
    }

}