用Kotlin协同器实现减速函数的测试

Question

我编写了一个非常简单的减速函数，可以用来在不阻塞的情况下减缓响应。

    suspend inline fun <T> slowdown(duration: Duration, block: () -> T): T {
        var result: T
        val timeTaken = measureTime {
            result = block()
        }
        delay(duration - timeTaken)
        return result
    }

在主工作中正确运行它。

fun main() = runBlocking {

    val timeTaken1 = measureTime {
        slowdown(2.seconds) {
            delay(1000)
        }
    }

    val timeTaken2 = measureTime {
        slowdown(2.seconds) {
            delay(4000)
        }
    }

    println(timeTaken1) // 2.008962891s
    println(timeTaken2) // 4.000145711s
    
}

现在，我想编写一个测试用例来测试经济放缓，但实际上不需要2秒或4秒。

    @Test
    @ExperimentalCoroutinesApi
    fun `ensure execution takes N seconds when operation takes N-t time`() = runTest {

        val timeTaken1 = measureTime {
            slowdown(2.seconds) {
                delay(1000)
            }
        }

        val timeTaken2 = measureTime {
            slowdown(2.seconds) {
                delay(4000)
            }
        }

        println("========")
        println(timeTaken1) // 9.472240ms
        println(timeTaken2) // 131.839us
        println("========")

    }

我假设measureTime和runTest玩得不好，但在delay上表现很好

如果我在测试中用Thread.sleep替换延迟

        val timeTaken1 = measureTime {
            slowdown(2.seconds) {
                Thread.sleep(1000)
            }
        }

        val timeTaken2 = measureTime {
            slowdown(2.seconds) {
                Thread.sleep(4000)
            }
        }

然后打印出来

========
1.008311216s
4.000221902s
========

delay(1000)在runTest下立即发生，但是measureTime也测量它是即时的，而不是被1秒所抵消。

我以为我可以用advanceTimeBy()破解它，但它似乎不影响measureTime。

将runTest更改为runBlocking是正确的，但它也会将测试速度分别降低到2秒和4秒。

是否有一个measureTime能很好地与runTest一起工作并在正常的runBlocking下工作？

Answer 1

suspend fun <T> slowdown(duration: Duration, block: suspend () -> T): T = coroutineScope {
    launch { delay(duration) }
    block()
}

@Test
@ExperimentalCoroutinesApi
fun `ensure execution takes N seconds when execution faster than N`() = runTest {
    val currentTime1 = currentTime
    slowdown(2.seconds) {
        delay(1.seconds)
    }
    val currentTime2 = currentTime
    assertEquals(2000, currentTime2 - currentTime1)
}

@Test
@ExperimentalCoroutinesApi
fun `ensure execution takes more than N seconds when execution slower than N`() = runTest {
    val currentTime1 = currentTime
    slowdown(1.seconds) {
        delay(2.seconds)
    }
    val currentTime2 = currentTime
    assertEquals(2000, currentTime2 - currentTime1)
}