Emit items with delay: 1 ... delay ... 2 ... delay ...

gistfile1.txt

    @Test
    fun testEmitWithDelays() {
        val DELAY = 500L
        val COUNT = 5

        val latch = CountDownLatch(1)
        val startMoment = System.currentTimeMillis()
        var endMoment : Long = 0

        Observable
                .range(0, COUNT)
                .flatMap( { Observable.just(it).delay(DELAY, TimeUnit.MILLISECONDS) }, 1) // maxConcurrent = 1
                .subscribe(
                        { println("... value: $it, ${System.currentTimeMillis() - startMoment}") },
                        {},
                        {
                            endMoment = System.currentTimeMillis()
                            latch.countDown()
                        })

        latch.await()
        assertTrue { endMoment - startMoment >= DELAY * COUNT }
    }