with-runTest

Code

package com.glassthought.sandbox

import com.glassthought.sandbox.impl.CustomDescribeSpec
import com.glassthought.sandbox.util.out.impl.out
import io.kotest.matchers.shouldBe
import kotlinx.coroutines.ExperimentalCoroutinesApi
import kotlinx.coroutines.launch
import kotlinx.coroutines.test.advanceTimeBy
import kotlinx.coroutines.test.advanceUntilIdle
import kotlinx.coroutines.test.runTest
import kotlin.time.Duration.Companion.milliseconds
import kotlin.time.Duration.Companion.seconds

/** Shows basics of using runTest so that functions like 'delay' become virtual timed. */
@OptIn(ExperimentalCoroutinesApi::class)
class VirtualTimeDescribeSpec : CustomDescribeSpec({

  describe("Timer Service") {

    it("should complete instantly with virtual time") {
      runTest {
        var done = false

        out.info("advanceUntilIdle() auto advances")
        launch {
          out.delay(5.seconds) // Would normally take 5 seconds

          done = true
        }

        // Time jumps forward instantly
        advanceUntilIdle()

        done shouldBe true
      }
    }

    it("should control time step by step") {
      runTest {
        var counter = 0

        out.info("advanceTimeBy() gives precise control.")

        launch {
          out.delay(1.seconds)
          counter++
          out.delay(1.seconds)
          counter++
        }

        advanceTimeBy(1100.milliseconds)
        counter shouldBe 1

        advanceTimeBy(1100.milliseconds)
        counter shouldBe 2
      }
    }
  }
})


private var count = 0
private suspend fun incrementCountAndPrint(string: String) {
  count += 1

  out.info("[${count}]: ${string}")
}

private suspend fun incrementAndPrintForIt(msg: String) {
  incrementCountAndPrint(msg)
  out.info("")
}

Command to reproduce:

gt.sandbox.checkout.commit 680dd5e9e988c8ebec90 \
&& cd "${GT_SANDBOX_REPO}" \
&& cmd.run.announce "./gradlew test --rerun-tasks"

Recorded output of command:

Picked up JAVA_TOOL_OPTIONS: -Dkotlinx.coroutines.debug
> Task :app:checkKotlinGradlePluginConfigurationErrors SKIPPED
> Task :app:processResources NO-SOURCE
> Task :app:processTestResources NO-SOURCE
> Task :app:compileKotlin
> Task :app:compileJava NO-SOURCE
> Task :app:classes UP-TO-DATE
> Task :app:compileTestKotlin
> Task :app:compileTestJava NO-SOURCE
> Task :app:testClasses UP-TO-DATE

> Task :app:test
Picked up JAVA_TOOL_OPTIONS: -Dkotlinx.coroutines.debug

Gradle Test Executor 1 STANDARD_OUT
    Warning: Kotest autoscan is enabled. This means Kotest will scan the classpath for extensions that are annotated with @AutoScan. To avoid this startup cost, disable autoscan by setting the system property 'kotest.framework.classpath.scanning.autoscan.disable=true'. In 6.0 this value will default to true. For further details see https://kotest.io/docs/next/framework/project-config.html#runtime-detection

com.glassthought.sandbox.VirtualTimeDescribeSpec > Timer Service > should complete instantly with virtual time STARTED

com.glassthought.sandbox.VirtualTimeDescribeSpec > Timer Service > should complete instantly with virtual time STANDARD_OUT
    [INFO][elapsed:   38ms][①][coroutname:@kotlinx.coroutines.test runner#5] advanceUntilIdle() auto advances
    [INFO][elapsed:   42ms][⓶][coroutname:@coroutine#6] [🐢] Delaying for [5s]
    [INFO][elapsed:   43ms][⓶][coroutname:@coroutine#6] Done delaying for [5s]

com.glassthought.sandbox.VirtualTimeDescribeSpec > Timer Service > should complete instantly with virtual time PASSED

com.glassthought.sandbox.VirtualTimeDescribeSpec > Timer Service > should control time step by step STARTED

com.glassthought.sandbox.VirtualTimeDescribeSpec > Timer Service > should control time step by step STANDARD_OUT
    [INFO][elapsed:   52ms][⓷][coroutname:@kotlinx.coroutines.test runner#8] advanceTimeBy() gives precise control.
    [INFO][elapsed:   52ms][⓸][coroutname:@coroutine#9] [🐢] Delaying for [1s]
    [INFO][elapsed:   52ms][⓸][coroutname:@coroutine#9] Done delaying for [1s]
    [INFO][elapsed:   52ms][⓸][coroutname:@coroutine#9] [🐢] Delaying for [1s]
    [INFO][elapsed:   52ms][⓸][coroutname:@coroutine#9] Done delaying for [1s]

com.glassthought.sandbox.VirtualTimeDescribeSpec > Timer Service > should control time step by step PASSED

BUILD SUCCESSFUL in 2s
3 actionable tasks: 3 executed