HairPullingTestSolution.kt

@RunWith(MockitoJUnitRunner::class)
class DemoViewModelTest {

    private var testScheduler = TestScheduler()
    @Test
    fun testVodoo() {
        val subject: PublishSubject<Int> = PublishSubject.create()
        val testObserver = subject
            .subscribeOn(testScheduler)
            .observeOn(testScheduler)
            .test()
        testScheduler.triggerActions()
        subject.onNext(1)
        testScheduler.triggerActions()
        testObserver.assertValueCount(1)
    }
}