Unit Test case - https://proandroiddev.com/unit-tests-with-dagger2-retrofit2-rxjava2-and-mockk-android-1c268fa77957

AppRepositoryInjectTest.kt

class AppRepositoryInjectTest {

    @Inject
    lateinit var appAPIs: AppAPIs

    @Before
    fun setUp() {
        val component = DaggerTestAppComponent.builder()
            .applicationModule(TestApplicationModule(GDelegate()))
            .build()
        component.into(this)
    }

    @Test
    fun `my test`() {
        assertNotNull(appAPIs)

        /* Given */
        every { appAPIs.getForecastTempWithUrl("r") } returns Flowable.just(APIResponse())

        /* When */
        val result = appAPIs.getForecastTempWithUrl("r")

        /* Then */
        result
            .test()
            .assertValue(APIResponse())
    }
}