Kotlin: How to convert test which uses Thread.sleep to RxJava TestScheduler - multithreading

Question

I am writing an instrumental test, it checks if when i cache something into a Rx buffer and after some interval(10 seconds) this Subject insert buffered values to my Room database.
The test is correct when I use Thread.sleep(syncTimeInterval). I want to write this same test using TestScheduler.
Here it is with Thread.sleep version(which pass the test):
#Test
fun testMultipleLogs() {
val loadAllCloudCallBefore = appDatabase.logCloudCallDao().loadAll()
val loadAllLogNewSessionBefore = appDatabase.logNewSessionDao().loadAll()
assertEquals(0, loadAllCloudCallBefore.size)
assertEquals(0, loadAllLogNewSessionBefore.size)
Observable.interval(1, TimeUnit.SECONDS)
.take(20)
.subscribe { logManager.logNewSession() }
Observable.interval(1, TimeUnit.SECONDS)
.take(20)
.subscribe { logManager.logCloudCall("url", "callgoup") }
Observable.interval(1, TimeUnit.SECONDS)
.take(20)
.subscribe { logManager.logNewSession() }
Observable.interval(1, TimeUnit.SECONDS)
.take(20)
.subscribe { logManager.logCloudCall("url", "callgoup") }
Observable.interval(1, TimeUnit.SECONDS)
.take(20)
.subscribe { logManager.logNewSession() }
Observable.interval(1, TimeUnit.SECONDS)
.take(20)
.subscribe { logManager.logCloudCall("url", "callgoup") }
Thread.sleep(30000)
val loadAllCloudCallAfter = appDatabase.logCloudCallDao().loadAll()
val loadAllLogNewSessionAfter = appDatabase.logNewSessionDao().loadAll()
assertEquals(60, loadAllCloudCallAfter.size)
assertEquals(60, loadAllLogNewSessionAfter.size)
}
And here, this test not passes, the size after expecting time advanced by TestScheduler is 0(not 60)
#Test
fun testMultipleLogs() {
var testScheduler: TestScheduler = TestScheduler()
val loadAllCloudCallBefore = appDatabase.logCloudCallDao().loadAll()
val loadAllLogNewSessionBefore = appDatabase.logNewSessionDao().loadAll()
assertEquals(0, loadAllCloudCallBefore.size)
assertEquals(0, loadAllLogNewSessionBefore.size)
Observable.interval(1, TimeUnit.SECONDS, testScheduler)
.take(20)
.subscribe { logManager.logNewSession() }
Observable.interval(1, TimeUnit.SECONDS, testScheduler)
.take(20)
.subscribe { logManager.logCloudCall("url", "callgoup") }
Observable.interval(1, TimeUnit.SECONDS, testScheduler)
.take(20)
.subscribe { logManager.logNewSession() }
Observable.interval(1, TimeUnit.SECONDS, testScheduler)
.take(20)
.subscribe { logManager.logCloudCall("url", "callgoup") }
Observable.interval(1, TimeUnit.SECONDS, testScheduler)
.take(20)
.subscribe { logManager.logNewSession() }
Observable.interval(1, TimeUnit.SECONDS, testScheduler)
.take(20)
.subscribe { logManager.logCloudCall("url", "callgoup") }
testScheduler.advanceTimeBy(21, TimeUnit.SECONDS)
val loadAllCloudCallAfter = appDatabase.logCloudCallDao().loadAll()
val loadAllLogNewSessionAfter = appDatabase.logNewSessionDao().loadAll()
assertEquals(60, loadAllCloudCallAfter.size)
assertEquals(60, loadAllLogNewSessionAfter.size)
}
How can i test this case properly? Is there a way?
UPDATE
The functions in LogManager looks like this:
fun logCloudCall(url: String, callGroup: String) {
val logCloudCall = LogCloudCall(url = url, callGroup = callGroup, date = Converter.GENERAL_DATE_FORMAT.format(Date()))
Log.v("LogManager", logCloudCall.toString())
addLog(logCloudCall)
}
fun logNewSession() {
val logNewSession =
LogNewSession(
date = Converter.GENERAL_DATE_FORMAT.format(Date()))
Log.v("LogManager", logNewSession.toString())
addLog(logNewSession)
}
fun addLog(logEvent: LogEvent) {
source.onNext(logEvent)
}
And this is the mechanism which i use in my LogManager init:
val source = PublishSubject.create<LogEvent>().toSerialized()
var logRepository: LogRepository
init {
logRepository = LogRepositoryImpl(context)
configureSubject()
}
fun configureSubject() {
source
.buffer(10, TimeUnit.SECONDS)
.subscribe { bufferedData -> proceedValues(bufferedData) }
}

Answer 1

The following test passes:
#Test
fun foo() {
val testScheduler = TestScheduler()
var count = 0
Observable.interval(1, TimeUnit.SECONDS, testScheduler)
.take(20)
.subscribe { count++ }
testScheduler.advanceTimeBy(21, SECONDS)
assert(count == 20)
}
That is, your test code looks correct, but the result is not correct. The only unknown here is the logManager code. Is there any threading in that class? That may explain why the count is still 0: you may have a race condition.
It's probably due to the buffer call. buffer internally uses the a computation Scheduler:
public final Observable<List<T>> buffer(long timespan, TimeUnit unit) {
return buffer(timespan, unit, Schedulers.computation(), Integer.MAX_VALUE);
}
This will probably result in the threading issue you're seeing.