TimeServiceKtTest.kt

import kotlinx.coroutines.delay
import kotlin.time.Duration.Companion.milliseconds
import kotlin.time.Duration.Companion.seconds

suspend fun multiplyWithDelay(a: Int, b: Int): Int {
    delay(10.seconds)
    return a * b 
}


data class Box(var value: Int)

suspend fun modify(box: Box) {
    box.value = 1
    delay(10.milliseconds)
    box.value = 2
    delay(20.milliseconds)
    box.value = 3
}

@OptIn(ExperimentalCoroutinesApi::class, ExperimentalTime::class)
class TimeServiceKtTest {
    @Test
    fun `multiply with delay`() = runTest {
        val time = measureTime {
            val res = multiplyWithDelay(2, 3)
            assertEquals(6, res)
        }
        println("Test took $time")
    }

    @Test
    fun `modify box`() = runTest {
        val box = Box(0)
        launch {
            modify(box)
        }

        Thread.sleep(100)
        assertEquals(0, box.value)

        runCurrent()
        assertEquals(1, box.value)

        advanceTimeBy(5.milliseconds)
        runCurrent()
        assertEquals(1, box.value)

        advanceTimeBy(5.milliseconds)
        runCurrent()
        assertEquals(2, box.value)

        advanceTimeBy(21.milliseconds)
//        runCurrent()
        assertEquals(3, box.value)

        advanceUntilIdle()
        assertEquals(3, box.value)

    }
}