Using Capture Slot fails on every second run of test

[owolp]

Prerequisites

Please answer the following questions for yourself before submitting an issue.

• I am running the latest version
• I checked the documentation and found no answer
• I checked to make sure that this issue has not already been filed

Expected Behavior

Tests should run with the same result all the time

Current Behavior

First tests always pass, but every second test fails

Steps to Reproduce

The bug appears after running test for more than one time - set repeat count of test for 2 or more.

Context

• MockK version: 1.10.2
• OS: MacOS
• Kotlin version: 1.4.10
• JDK version: openjdk8
• JUnit version: 4.13.1
• Type of test: unit test

Stack trace

---==START==---
{MODEL=Mazda}
Mazda
null
---==END==---
---==START==---
{MODEL=Mazda, YEAR=2000}
Mazda

junit.framework.AssertionFailedError
	at junit.framework.Assert.fail(Assert.java:55)
	at junit.framework.Assert.assertTrue(Assert.java:22)
	at junit.framework.Assert.assertFalse(Assert.java:39)
	at junit.framework.Assert.assertFalse(Assert.java:47)
	at de.smyle.core.analytics.domain.usecase.event.SendEventTest.test With Null(Test.kt:98)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63)
	at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329)
	at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293)
	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:413)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:40)
	at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230)
	at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58)

---==START==---
{MODEL=Mazda, YEAR=2000}
Mazda

junit.framework.AssertionFailedError
	at junit.framework.Assert.fail(Assert.java:55)
	at junit.framework.Assert.assertTrue(Assert.java:22)
	at junit.framework.Assert.assertFalse(Assert.java:39)
	at junit.framework.Assert.assertFalse(Assert.java:47)
	at de.smyle.core.analytics.domain.usecase.event.SendEventTest.test With Null(Test.kt:98)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63)
	at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329)
	at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293)
	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:413)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:40)
	at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230)
	at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58)

---==START==---
{MODEL=Mazda, YEAR=2000}
Mazda

junit.framework.AssertionFailedError
	at junit.framework.Assert.fail(Assert.java:55)
	at junit.framework.Assert.assertTrue(Assert.java:22)
	at junit.framework.Assert.assertFalse(Assert.java:39)
	at junit.framework.Assert.assertFalse(Assert.java:47)
	at de.smyle.core.analytics.domain.usecase.event.SendEventTest.test With Null(Test.kt:98)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63)
	at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329)
	at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293)
	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:413)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:40)
	at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230)
	at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58)

---==START==---
{MODEL=Mazda, YEAR=2000}
Mazda

junit.framework.AssertionFailedError
	at junit.framework.Assert.fail(Assert.java:55)
	at junit.framework.Assert.assertTrue(Assert.java:22)
	at junit.framework.Assert.assertFalse(Assert.java:39)
	at junit.framework.Assert.assertFalse(Assert.java:47)
	at de.smyle.core.analytics.domain.usecase.event.SendEventTest.test With Null(Test.kt:98)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63)
	at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329)
	at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293)
	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:413)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:40)
	at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230)
	at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58)


Process finished with exit code 255

Minimal reproducible code (the gist of this issue)

interface Event {
    val params: Map<String, Any?>
}

enum class MyEvent(
    override val params: MutableMap<String, Any?> = mutableMapOf()
) : Event {

    FirstEvent
}

class Repository {

    fun sendEvent(analyticsEvent: Event) {
        println(analyticsEvent.params)
    }
}

class SendEvent(
    private val repository: Repository
) {

    companion object {
        const val MODEL = "MODEL"
        const val YEAR = "YEAR"
    }

    operator fun invoke(
        model: String,
        year: String?
    ) {
        val event = MyEvent.FirstEvent

        event.params[MODEL] = model

        if (year != null) {
            event.params[YEAR] = year
        }

        repository.sendEvent(event)
    }
}

class SendEventTest {

    private val analyticsRepository = mockk<Repository>()

    private lateinit var sut: SendEvent

    @Before
    fun setup() {
        sut = SendEvent(analyticsRepository)
    }

    @Test
    fun `test With Not Null`() {
        val slot = slot<MyEvent>()
        every { analyticsRepository.sendEvent(analyticsEvent = capture(slot)) } just Runs

        val model = "Mazda"
        val year = "2000"

        sut(model, year)

        with(slot.captured.params) {
            assertEquals("Mazda", this["MODEL"])
            assertEquals("2000", this["YEAR"])
        }
    }

    @Test
    fun `test With Null`() {
        val slot = slot<MyEvent>()
        every { analyticsRepository.sendEvent(analyticsEvent = capture(slot)) } just Runs

        val model = "Mazda"
        val year: String? = null

        sut(model, year)

        with(slot.captured.params) {
            assertEquals("Mazda", this["MODEL"])
            println(this["MODEL"])
            assertFalse(this.containsKey("YEAR"))
            println(this["YEAR"])
        }
    }
}

[Raibaz]

How are you handling test repetition? I tried reproducing this with @RepeatedTest(3) on both tests and it passes correctly all three times.

[owolp]

I've used the build-in feature of InteliJ/AS

Goto "Run / Debug Configuration" and select the desired test run of choice or create a new test run. Under Configuration you can set it up to repeat "N Times", "Until Failure" or "Until Success".

https://imgur.com/37Ce5p1
https://imgur.com/dNZ2gYa

Also, please note that in order to reproduce the issue you should run the class tests. Tests pass all the time, if they are run individually for N times.

[Raibaz]

Ok thanks, I have been able to reproduce it now.

I have been digging a bit in the code and it seems to be happening because when the method call is being intercepted the wrong handler is returned at this line.

The reason why this happens, though, is beyond my knowledge of the internals of mockk. Perhaps @oleksiyp knows better.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions. If you are sure that this issue is important and should not be marked as stale just ask to put an important label.

[owolp]

The bug is still reproducible in recent versions. Can we put the important label on it?

[owolp]

The issue is not related to the mockk library at all. MyEvent is an enum class and acts as a singleton. More info can be found on Java Singletons Using Enum.

Closing the issue.