Coroutine Debugging

kotlinx-coroutines-debug is a module that provides debugging capabilities for coroutines on the JVM. When enabled, a debug agent is installed by ByteBuddy and captures information on coroutines as they are created, started, suspended and resumed.

Kotest provides the ability to enable debugging per test. We can do this by enabling coroutineDebugProbes in test config.

Once enabled, any coroutines launched inside the test will be included in a "coroutine dump" after the test completes, or as soon as an exception is thrown.

class CoroutineDebugging : FunSpec() {
   init {
      test("foo").config(coroutineDebugProbes = true) {
         someMethodThatLaunchesACoroutine() // launches a new coroutine
      }
   }
}

The coroutine dump will look something like:

Coroutines dump 2021/11/27 22:17:43

Coroutine DeferredCoroutine{Active}@71f1906, state: CREATED
    (Coroutine creation stacktrace)
    at kotlin.coroutines.intrinsics.IntrinsicsKt__IntrinsicsJvmKt.createCoroutineUnintercepted(IntrinsicsJvm.kt:122)
    at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable(Cancellable.kt:30)
    at kotlinx.coroutines.BuildersKt__Builders_commonKt.async$default(Builders.common.kt:82)
    at kotlinx.coroutines.BuildersKt.async$default(Unknown Source)
    at com.sksamuel.kotest.engine.coroutines.Wibble$1.invokeSuspend(CoroutineDebugTest.kt:37)
    at com.sksamuel.kotest.engine.coroutines.Wibble$1.invoke(CoroutineDebugTest.kt)

Spec level config

Coroutine debugging can be enabled for all tests in a spec by overriding the coroutineDebugProbes setting inside a spec:

class CoroutineDebugging : FunSpec() {
  init {

    coroutineDebugProbes = true

    test("foo") {
      // debugging enabled here
    }

    test("bar") {
      // debugging enabled here
    }

  }
}

Project wide config

Coroutine debugging can be enabled for all tests in a project by using ProjectConfig:

class ProjectConfig : AbstractProjectConfig() {
  override val coroutineDebugProbes = true
}