Test rx java return

MainPresenterTest.kt

@Test
fun `test fetchDataViaRX with an empty result`() {
    every { dataRepository.fetchDataWithRX() } returns Single.just(listOf())
    mainPresenter.fetchData()

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

    verify(exactly = 1) { view.onResult(capture(captureData)) }
    captureData.captured.let { res ->
        assertNotNull(res)
        assert(res.isEmpty())
    }
}