PublishSubjectTestRight.kt

val testPublisher = PublishSubject.create<String>()

var value:String = "initial"

fun myRxFunction(ioThread:Scheduler,mainThread:Scheduler){
  testPublisher
    .subscribeOn(ioThread)
    .observeOn(mainThread)
    .subscribe{
      saveString(it)
    }
}

fun saveString(message:String){
  value = message
}

@Test
fun myRxFunctionTest(){
  val testString = "test"
  val testScheduler = TestScheduler()
  
  myRxFunction(testScheduler,testScheduler)
  
  testScheduler.triggerActions()
  
  testPublisher.onNext(testString)
  
  assertEquals(value,testString)
}