PresenterWithDI.kt

class PresenterWithDI(
  private val networking: NetworkWrapper,
  private val crashReporting: CrashReporting
) {
  fun onSaveClicked() {
    val (response, error) = networking.callTheApi()
    if (error != null) 
      crashReporting.log("Oh no")
    else
      Log.d("DI", "Yay")
  }
}

PresenterWithDITest.kt

class PresenterWithDITest {
  private val mockNetworking = mock<NetworkWrapper>()
  private val mockCrashReporting = mock<CrashReporting>()
  
  private var presenter = PresenterWithDI(mockNetworking, mockCrashReporting)
  
  @Test
  fun networkError_onSaveClicked_logCrash() {
    //given
    when(mockNetworking.callTheApi()).thenReturn(null to ApiWentDownException("pretent API wen't down"))
    
    //when
    presenter.onSaveClicked()
    
    //then
    verify(mockCrashReporting).log("Oh no")
  }
}

PresenterWithoutDI.kt

class PresenterWithoutDI {
  private val networking: NetworkWrapper = NetworkWrapperImpl()
  private val crashReporting: CrashReporting = CrashReporting.getInstance()
  
  
  fun onSaveClicked() {
    val (response, error) = networking.callTheApi()
    if (error != null) 
      crashReporting.log("Oh no")
    else
      Log.d("DI", "Yay")
  }
}