Test fetchDataViaCallback()

MainPresenterTest.kt

@Test
fun `test fetchDataViaCallback with an result`() {
    val captureCallback = slot<(data: List<DataModel>) -> Unit>()
    every { dataRepository.fetchData(capture(captureCallback)) } answers {
        val fakeList = listOf(DataModel(1, "Value 1"))
        captureCallback.captured.invoke(fakeList)
    }
    mainPresenter.fetchDataViaCallback()

    val captureData = slot<List<UiDataModel>>()

    verify(exactly = 1) { view.onResult(capture(captureData)) }
    captureData.captured.let { res ->
        assertNotNull(res)
        assert(res.isNotEmpty())
        assertEquals("Value 1", res.first().value)
    }
}