InterfaceSegregationTest.kt

import com.nhaarman.mockito_kotlin.mock
import com.nhaarman.mockito_kotlin.times
import com.nhaarman.mockito_kotlin.verify
import org.junit.Test

class InterfaceSegregationTest {

    val mock = mock<()->Unit>()

    @Test
    fun `test for EventListener`() {

        val eventTrigger = EventTrigger()

        eventTrigger.setEventListener {
            onEventType_1 { mock() }
        }

        eventTrigger.triggerEventType1()

        verify(mock, times(1)).invoke()

    }

}

interface EventListener {

    fun onEventType_1(s: String)
    fun onEventType_3(s: String)
    fun onEventType_2(s: String)

}

class EventListenerImpl : EventListener {

    private var onEventType_1: ((s: String) -> Unit)? = null
    private var onEventType_2: ((s: String) -> Unit)? = null
    private var onEventType_3: ((s: String) -> Unit)? = null

    fun onEventType_1(f: (s: String) -> Unit) { onEventType_1 = f }
    fun onEventType_3(f: (s: String) -> Unit) { onEventType_2 = f }
    fun onEventType_2(f: (s: String) -> Unit) { onEventType_3 = f }

    override fun onEventType_1(s: String) { onEventType_1?.invoke(s) }
    override fun onEventType_2(s: String) { onEventType_2?.invoke(s) }
    override fun onEventType_3(s: String) { onEventType_3?.invoke(s) }
}

fun EventTrigger.setEventListener(init: EventListenerImpl.() -> Unit) {
    val listener = EventListenerImpl()
    listener.init()
    eventListener = listener
}

class EventTrigger(var eventListener: EventListener? = null) {

    fun triggerEventType1() {
        eventListener?.onEventType_1("event 1")
    }

}