mockk: Bug[Hard]: "Can't instantiate proxy for class kotlin.Any" when setting up mock on macOS

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

I have a test case like this:

it("forwards accepted values to all connected ports") {
    val port = createDummy()
    val connectedPorts = Array(5) {
        mockk<StandardPort<Any>>().also { mock ->
            every { mock.id } returns "Port $it"
            coEvery { mock.accept(any()) } just Runs
            port join mock
        }
    }

    // ...
}

I expect that mockk is able to produce mocks that I can use in the rest of the test and make assertions against. I expect this works on all platforms.

Current Behavior

On my Windows development machine this works fine. On my MacBook it throws an exception: io.mockk.MockKException: Can't instantiate proxy for class kotlin.Any which seems to be caused by the line coEvery { mock.accept(any()) } just Runs.

Steps to Reproduce

This issue is hard to reproduce. As stated, it only occurs on my MacBook. Additionally, it only occurs when running normally (not debugging). I tried to write another test case to isolate the issue, but it’s strange:

Given this real test case:

it("forwards accepted values to all connected ports") {
    val port = createDummy()
    val connectedPorts = Array(5) {
        mockk<StandardPort<Any>>().also { mock ->
            every { mock.id } returns "Port $it"
            coEvery { mock.accept(any()) } just Runs
            port join mock
        }
    }

    val value = Object()
    runBlocking { port.forward(value) }

    connectedPorts.forEach {
        coVerify(exactly = 1) { it.accept(value) }
    }
}

And this dummy test case to try to isolate the problem:

it("temp") {
    class Foo {
        fun accept(obj: Object): Unit = TODO()
    }
    val foo = mockk<Foo>()
    coEvery { foo.accept(any()) } just Runs
}

I find that:

• if the dummy test case is written above the real test case (and consequently runs first), no issues occur and all test cases pass
• if I write the dummy test case below the real test case, the dummy test case passes and the real test case fails

I noticed in the stacktrace that weakmaps are involved. Seems like some issue with initially populating that map, or maybe because it only holds references weakly something it references gets prematurely GC’d? Might also be a race condition.

Context

Please provide any relevant information about your setup. This is important in case the issue is not reproducible except for under certain conditions.

• MockK version: 1.8.10.kotlin13
• OS: macOS Mojave Version 10.14
• Kotlin version: 1.3.0
• JDK version: 9.0.1 (Oracle Corporation 9.0.1+11)
• JUnit version: jUnit 5
• Type of test: unit test

Stack trace

Running $ gradle clean test --info, I see this warning included in the output:

com.mycompany.testmaster.domain.StandardPortTests > Scenario: forwards accepted values to all connected ports STANDARD_ERROR
    [kotlintest-test-executor-0] WARN io.mockk.proxy.jvm.transformation.InliningClassTransformer - Failed to transform class java/lang/Object
    java.lang.NoClassDefFoundError: java/lang/AutoCloseable (wrong name: java/lang/WeakPairMap$Pair$Weak)
        at java.base/java.lang.WeakPairMap$Pair.weak(WeakPairMap.java:201)
        at java.base/java.lang.WeakPairMap.putIfAbsent(WeakPairMap.java:123)
        at java.base/java.lang.Module.implAddReads(Module.java:396)
        at java.base/java.lang.Module.implAddReads(Module.java:357)
        at java.base/java.lang.System$2.addReads(System.java:2146)
        at java.base/jdk.internal.module.Modules.addReads(Modules.java:85)
        at java.base/java.lang.reflect.Proxy$ProxyBuilder.lambda$getDynamicModule$4(Proxy.java:884)
        at java.base/jdk.internal.loader.AbstractClassLoaderValue$Memoizer.get(AbstractClassLoaderValue.java:327)
        at java.base/jdk.internal.loader.AbstractClassLoaderValue.computeIfAbsent(AbstractClassLoaderValue.java:203)
        at java.base/java.lang.reflect.Proxy$ProxyBuilder.getDynamicModule(Proxy.java:875)
        at java.base/java.lang.reflect.Proxy$ProxyBuilder.mapToModule(Proxy.java:814)
        at java.base/java.lang.reflect.Proxy$ProxyBuilder.<init>(Proxy.java:631)
        at java.base/java.lang.reflect.Proxy$ProxyBuilder.<init>(Proxy.java:636)
        at java.base/java.lang.reflect.Proxy.lambda$getProxyConstructor$0(Proxy.java:415)
        at java.base/jdk.internal.loader.AbstractClassLoaderValue$Memoizer.get(AbstractClassLoaderValue.java:327)
        at java.base/jdk.internal.loader.AbstractClassLoaderValue.computeIfAbsent(AbstractClassLoaderValue.java:203)
        at java.base/java.lang.reflect.Proxy.getProxyConstructor(Proxy.java:413)
        at java.base/java.lang.reflect.Proxy.newProxyInstance(Proxy.java:999)
        at java.base/sun.reflect.annotation.AnnotationParser$1.run(AnnotationParser.java:305)
        at java.base/sun.reflect.annotation.AnnotationParser$1.run(AnnotationParser.java:303)
        at java.base/java.security.AccessController.doPrivileged(Native Method)
        at java.base/sun.reflect.annotation.AnnotationParser.annotationForMap(AnnotationParser.java:303)
        at java.base/sun.reflect.annotation.AnnotationParser.parseAnnotation2(AnnotationParser.java:293)
        at java.base/sun.reflect.annotation.AnnotationParser.parseAnnotations2(AnnotationParser.java:120)
        at java.base/sun.reflect.annotation.AnnotationParser.parseAnnotations(AnnotationParser.java:72)
        at java.base/java.lang.reflect.Executable.declaredAnnotations(Executable.java:605)
        at java.base/java.lang.reflect.Executable.declaredAnnotations(Executable.java:603)
        at java.base/java.lang.reflect.Executable.getDeclaredAnnotations(Executable.java:591)
        at java.base/java.lang.reflect.Constructor.getDeclaredAnnotations(Constructor.java:579)
        at net.bytebuddy.description.method.MethodDescription$ForLoadedConstructor.getDeclaredAnnotations(MethodDescription.java:956)
        at net.bytebuddy.description.method.MethodDescription$AbstractBase.asToken(MethodDescription.java:732)
        at net.bytebuddy.description.method.MethodDescription$AbstractBase.asToken(MethodDescription.java:349)
        at net.bytebuddy.description.method.MethodList$AbstractBase.asTokenList(MethodList.java:53)
        at net.bytebuddy.dynamic.scaffold.InstrumentedType$Factory$Default$1.represent(InstrumentedType.java:317)
        at net.bytebuddy.ByteBuddy.redefine(ByteBuddy.java:716)
        at net.bytebuddy.ByteBuddy.redefine(ByteBuddy.java:691)
        at io.mockk.proxy.jvm.transformation.InliningClassTransformer.transform(InliningClassTransformer.kt:70)
        at java.instrument/java.lang.instrument.ClassFileTransformer.transform(ClassFileTransformer.java:246)
        at java.instrument/sun.instrument.TransformerManager.transform(TransformerManager.java:188)
        at java.instrument/sun.instrument.InstrumentationImpl.transform(InstrumentationImpl.java:550)
        at java.instrument/sun.instrument.InstrumentationImpl.retransformClasses0(Native Method)
        at java.instrument/sun.instrument.InstrumentationImpl.retransformClasses(InstrumentationImpl.java:157)
        at io.mockk.proxy.jvm.transformation.InlineInstrumentation.execute(InlineInstrumentation.kt:39)
        at io.mockk.proxy.jvm.ProxyMaker.inline(ProxyMaker.kt:88)
        at io.mockk.proxy.jvm.ProxyMaker.proxy(ProxyMaker.kt:30)
        at io.mockk.impl.instantiation.JvmMockFactory.newProxy(JvmMockFactory.kt:34)
        at io.mockk.impl.instantiation.AbstractMockFactory.newProxy$default(AbstractMockFactory.kt:28)
        at io.mockk.impl.instantiation.AbstractMockFactory.mockk(AbstractMockFactory.kt:53)
        at com.mycompany.testmaster.domain.StandardPortTests$1$1$6.invoke(StandardPortTests.kt:140)
        at com.mycompany.testmaster.domain.StandardPortTests$1$1$6.invoke(StandardPortTests.kt:15)
        at io.kotlintest.runner.jvm.TestCaseExecutor$executeTestSet$$inlined$map$lambda$1.call(TestCaseExecutor.kt:104)
        at io.kotlintest.runner.jvm.TestCaseExecutor$executeTestSet$$inlined$map$lambda$1.call(TestCaseExecutor.kt:23)
        at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
        at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
        at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
        at java.base/java.lang.Thread.run(Thread.java:844)

Followed later by the stacktrace of the failing test:

com.mycompany.testmaster.domain.StandardPortTests > Describe: Standard port FAILED
    io.mockk.MockKException: Can't instantiate proxy for class kotlin.Any
        at io.mockk.impl.instantiation.JvmMockFactory.newProxy(JvmMockFactory.kt:64)
        at io.mockk.impl.instantiation.AbstractMockFactory.newProxy$default(AbstractMockFactory.kt:28)
        at io.mockk.impl.instantiation.AbstractMockFactory.mockk(AbstractMockFactory.kt:53)
        at io.mockk.impl.stub.MockKStub$childMockK$$inlined$synchronized$lambda$1$1.invoke(MockKStub.kt:142)
        at io.mockk.impl.stub.MockKStub$childMockK$$inlined$synchronized$lambda$1$1.invoke(MockKStub.kt:8)
        at io.mockk.impl.InternalPlatform.customComputeIfAbsent(InternalPlatform.kt:44)
        at io.mockk.impl.stub.MockKStub$childMockK$$inlined$synchronized$lambda$1.invoke(MockKStub.kt:141)
        at io.mockk.impl.recording.CommonCallRecorder.safeExec(CommonCallRecorder.kt:66)
        at io.mockk.impl.log.SafeToString.exec(SafeToString.kt:10)
        at io.mockk.impl.stub.MockKStub.childMockK(MockKStub.kt:140)
        at io.mockk.impl.recording.PermanentMocker.permamentize(PermanentMocker.kt:48)
        at io.mockk.impl.recording.PermanentMocker.mock(PermanentMocker.kt:24)
        at io.mockk.impl.recording.states.RecordingState.mockPermanently(RecordingState.kt:120)
        at io.mockk.impl.recording.states.RecordingState.round(RecordingState.kt:32)
        at io.mockk.impl.recording.CommonCallRecorder.round(CommonCallRecorder.kt:45)
        at io.mockk.impl.eval.RecordedBlockEvaluator.record(RecordedBlockEvaluator.kt:47)
        at io.mockk.impl.eval.EveryBlockEvaluator.every(EveryBlockEvaluator.kt:25)
        at io.mockk.MockKDsl.internalCoEvery(API.kt:99)
        at io.mockk.MockKKt.coEvery(MockK.kt:115)
        at com.mycompany.testmaster.domain.StandardPortTests$1$1$6.invoke(StandardPortTests.kt:47)
        at com.mycompany.testmaster.domain.StandardPortTests$1$1$6.invoke(StandardPortTests.kt:15)

        Caused by:
        io.mockk.proxy.MockKAgentException: Failed to subclass class java.lang.Object
            at io.mockk.proxy.jvm.ProxyMaker.proxy(ProxyMaker.kt:38)
            at io.mockk.impl.instantiation.JvmMockFactory.newProxy(JvmMockFactory.kt:34)
            ... 20 more

            Caused by:
            java.lang.IllegalArgumentException: Could not create type
                at net.bytebuddy.TypeCache.findOrInsert(TypeCache.java:139)
                at net.bytebuddy.TypeCache.findOrInsert(TypeCache.java:159)
                at io.mockk.proxy.jvm.transformation.SubclassInstrumentation.subclass(SubclassInstrumentation.kt:46)
                at io.mockk.proxy.jvm.ProxyMaker.subclass(ProxyMaker.kt:110)
                at io.mockk.proxy.jvm.ProxyMaker.proxy(ProxyMaker.kt:35)
                ... 21 more

                Caused by:
                java.lang.NoClassDefFoundError: java/lang/AutoCloseable (wrong name: java/lang/WeakPairMap$Pair$Weak)
                    at java.base/java.lang.WeakPairMap$Pair.weak(WeakPairMap.java:201)
                    at java.base/java.lang.WeakPairMap.putIfAbsent(WeakPairMap.java:123)
                    at java.base/java.lang.Module.implAddReads(Module.java:396)
                    at java.base/java.lang.Module.implAddReads(Module.java:357)
                    at java.base/java.lang.System$2.addReads(System.java:2146)
                    at java.base/jdk.internal.module.Modules.addReads(Modules.java:85)
                    at java.base/java.lang.reflect.Proxy$ProxyBuilder.lambda$getDynamicModule$4(Proxy.java:884)
                    at java.base/jdk.internal.loader.AbstractClassLoaderValue$Memoizer.get(AbstractClassLoaderValue.java:327)
                    at java.base/jdk.internal.loader.AbstractClassLoaderValue.computeIfAbsent(AbstractClassLoaderValue.java:203)
                    at java.base/java.lang.reflect.Proxy$ProxyBuilder.getDynamicModule(Proxy.java:875)
                    at java.base/java.lang.reflect.Proxy$ProxyBuilder.mapToModule(Proxy.java:814)
                    at java.base/java.lang.reflect.Proxy$ProxyBuilder.<init>(Proxy.java:631)
                    at java.base/java.lang.reflect.Proxy$ProxyBuilder.<init>(Proxy.java:636)
                    at java.base/java.lang.reflect.Proxy.lambda$getProxyConstructor$0(Proxy.java:415)
                    at java.base/jdk.internal.loader.AbstractClassLoaderValue$Memoizer.get(AbstractClassLoaderValue.java:327)
                    at java.base/jdk.internal.loader.AbstractClassLoaderValue.computeIfAbsent(AbstractClassLoaderValue.java:203)
                    at java.base/java.lang.reflect.Proxy.getProxyConstructor(Proxy.java:413)
                    at java.base/java.lang.reflect.Proxy.newProxyInstance(Proxy.java:999)
                    at java.base/sun.reflect.annotation.AnnotationParser$1.run(AnnotationParser.java:305)
                    at java.base/sun.reflect.annotation.AnnotationParser$1.run(AnnotationParser.java:303)
                    at java.base/java.security.AccessController.doPrivileged(Native Method)
                    at java.base/sun.reflect.annotation.AnnotationParser.annotationForMap(AnnotationParser.java:303)
                    at java.base/sun.reflect.annotation.AnnotationParser.parseAnnotation2(AnnotationParser.java:293)
                    at java.base/sun.reflect.annotation.AnnotationParser.parseAnnotations2(AnnotationParser.java:120)
                    at java.base/sun.reflect.annotation.AnnotationParser.parseAnnotations(AnnotationParser.java:72)
                    at java.base/java.lang.reflect.Executable.declaredAnnotations(Executable.java:605)
                    at java.base/java.lang.reflect.Executable.declaredAnnotations(Executable.java:603)
                    at java.base/java.lang.reflect.Executable.getDeclaredAnnotations(Executable.java:591)
                    at java.base/java.lang.reflect.Constructor.getDeclaredAnnotations(Constructor.java:579)
                    at net.bytebuddy.description.method.MethodDescription$ForLoadedConstructor.getDeclaredAnnotations(MethodDescription.java:956)
                    at net.bytebuddy.description.method.MethodDescription$TypeSubstituting.getDeclaredAnnotations(MethodDescription.java:1423)
                    at net.bytebuddy.description.method.MethodDescription$AbstractBase.asToken(MethodDescription.java:732)
                    at net.bytebuddy.description.method.MethodDescription$AbstractBase.asToken(MethodDescription.java:349)
                    at net.bytebuddy.description.method.MethodList$AbstractBase.asTokenList(MethodList.java:53)
                    at net.bytebuddy.dynamic.scaffold.subclass.ConstructorStrategy$Default$5.doExtractConstructors(ConstructorStrategy.java:160)
                    at net.bytebuddy.dynamic.scaffold.subclass.ConstructorStrategy$Default.extractConstructors(ConstructorStrategy.java:179)
                    at net.bytebuddy.dynamic.scaffold.subclass.SubclassDynamicTypeBuilder.applyConstructorStrategy(SubclassDynamicTypeBuilder.java:204)
                    at net.bytebuddy.dynamic.scaffold.subclass.SubclassDynamicTypeBuilder.make(SubclassDynamicTypeBuilder.java:179)
                    at net.bytebuddy.dynamic.scaffold.subclass.SubclassDynamicTypeBuilder.make(SubclassDynamicTypeBuilder.java:172)
                    at net.bytebuddy.dynamic.DynamicType$Builder$AbstractBase.make(DynamicType.java:3121)
                    at net.bytebuddy.dynamic.DynamicType$Builder$AbstractBase$Delegator.make(DynamicType.java:3258)
                    at io.mockk.proxy.jvm.transformation.SubclassInstrumentation.doInterceptedSubclassing(SubclassInstrumentation.kt:79)
                    at io.mockk.proxy.jvm.transformation.SubclassInstrumentation.access$doInterceptedSubclassing(SubclassInstrumentation.kt:17)
                    at io.mockk.proxy.jvm.transformation.SubclassInstrumentation$subclass$1.call(SubclassInstrumentation.kt:49)
                    at io.mockk.proxy.jvm.transformation.SubclassInstrumentation$subclass$1.call(SubclassInstrumentation.kt:17)
                    at net.bytebuddy.TypeCache.findOrInsert(TypeCache.java:137)
                    ... 25 more

// -----------------------[ GRADLE DEFINITIONS ] -----------------------

Root project definitions:

import org.jetbrains.kotlin.gradle.tasks.KotlinCompile

plugins {
    kotlin("jvm") version "1.3.0" apply false
    kotlin("kapt") version "1.3.0" apply false
    id("org.jlleitschuh.gradle.ktlint") version "6.2.0" apply false
    id("com.adarshr.test-logger") version "1.5.0"
    `build-scan`
}

allprojects {
    group = "com.mycompany.testmaster"
    version = "0.1.0"

    repositories {
        jcenter()
        mavenCentral()
    }
}

subprojects {
    apply(plugin = "org.jlleitschuh.gradle.ktlint")
    apply(plugin = "com.adarshr.test-logger")

    tasks.withType<Test> {
        useJUnitPlatform()

        testLogging {
            events("PASSED", "FAILED", "SKIPPED")
        }

        testlogger {
            setTheme("mocha")
        }
    }

    tasks.withType<KotlinCompile> {
        kotlinOptions.jvmTarget = "1.8"
    }
}

buildScan {
    setTermsOfServiceUrl("https://gradle.com/terms-of-service")
    setTermsOfServiceAgree("yes")
    setAllowUntrustedServer(true)
}

Sub-project definitions:

plugins {
    kotlin("jvm")
}

dependencies {
    implementation(kotlin("stdlib-jdk8"))
    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.0.0")
    implementation("io.github.microutils:kotlin-logging:1.6.10")

    testImplementation("io.kotlintest:kotlintest-runner-junit5:3.1.9")
    testImplementation("io.mockk:mockk:1.8.10.kotlin13")
    testImplementation("org.slf4j:slf4j-api:1.7.25")
    testImplementation("org.slf4j:slf4j-simple:1.7.25")
}