Mocking methods with inline class return type

[nyarian]

The issue

Seems that here are some issues with inline classes returning using returns infix function, but I am not sure if it's actually an issue inside Mockk.
When I'm trying to return a response wrapped with inline class type ClassCastException happens.
After inline modifier removal on class definition all works fine.
Here is the code:

Test method part:
every { refToObjectThatHasInlineClassReturnType.method(any()) } returns ResponseCode(0)

Invoked method's part that actually returns a wrapped type:

fun method(): ResponseCode { return ResponseCode(/*value*/) }

The inline class itself:

inline class ResponseCode(private val value: Int) { val isSuccessful: Boolean get() = value == SOME_CONSTANT }

Steps to Reproduce

1. Create an inline class
2. Make a return type of any method to be this inline class'es type
3. Mock the method to return "an instance" of this type

Context

• MockK version: 1.9.kotlin12
• OS: Ubuntu 18.04 (Linux 4.15.0-45-generic amd64)
• Kotlin version: 1.3.20
• JDK version: 1.8.0_152-release
• JUnit version: 4.12
• Unit test

Stack trace

// -----------------------[ YOUR STACK STARTS HERE ] -----------------------
java.lang.ClassCastException: package.ResponseCode cannot be cast to java.lang.Integer

	at package.ClassThatReturnsInlineClass.method$module_debug(ClassThatReturnsInlineClass.kt:11)
	at package.CallingClass.someOtherMethod(CallingClass.kt:57)
	at package.CallingClass.someOtherMethod2(CallingClass.kt:45)
	at package.CallingClass.someOtherMethod3(CallingClass.kt:28)
	at package.TestClass$testMethod$2.invokeSuspend(TestClass.kt:109)
	at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:32)
	at kotlinx.coroutines.DispatchedTask.run(Dispatched.kt:236)
	at kotlinx.coroutines.EventLoopBase.processNextEvent(EventLoop.kt:123)
	at kotlinx.coroutines.BlockingCoroutine.joinBlocking(Builders.kt:69)
	at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking(Builders.kt:45)
	at kotlinx.coroutines.BuildersKt.runBlocking(Unknown Source)
	at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking$default(Builders.kt:35)
	at kotlinx.coroutines.BuildersKt.runBlocking$default(Unknown Source)
	at package.TestClass.testMethod(TestClass.kt:109)
	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:50)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
	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.runLeaf(ParentRunner.java:325)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
	at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
	at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
	at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
	at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
	at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
	at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
Caused by: java.lang.ClassCastException: kotlin.Unit cannot be cast to java.lang.Void
	at eu.example.schedule.kafka.KafkaAdminImplTest$mockkVoidReturnFails$1.invoke(KafkaAdminImplTest.kt:87)
	at eu.example.schedule.kafka.KafkaAdminImplTest$mockkVoidReturnFails$1.invoke(KafkaAdminImplTest.kt:24)
	at io.mockk.impl.eval.RecordedBlockEvaluator$record$block$1.invoke(RecordedBlockEvaluator.kt:22)
	at io.mockk.impl.recording.JvmAutoHinter.autoHint(JvmAutoHinter.kt:23)
	at io.mockk.impl.eval.RecordedBlockEvaluator.record(RecordedBlockEvaluator.kt:31)
	... 25 more

Dependency definition

// -----------------------[ GRADLE DEFINITIONS ] -----------------------
dependencies {
    //...
    testImplementation "io.mockk:mockk:$mockk_version"
    //...
}

whereas mockk_version property has a value of 1.9.kotlin12

[robsn]

Same problem occurs for me with 1.9.2

[oleksiyp]

Inline classes are not supported

[mkobit]

Is there another issue tracking and what needs to happen to support inline class?

[oleksiyp]

Check #152. There is kind of workaround. Don't know if it works

[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 put an important tag.

[oleksiyp]

Don't reopen in favour of #152

[tomyuval]

@oleksiyp, this seems to still have not been solved in 1.10.0. Also, #152 is about receiving a parameter of an inline class type, whereas this issue is about a return value of an inline class type, so maybe this issue should be reopened? (Note in particular that the workaround mentioned in #152 - namely not passing any() directly, but wrapped in a call to the inline class's constructor - is not applicable for the case of returning a value of an inline class type.)

[tomyuval]

Hey, @oleksiyp, any news about this issue? Anything we can do to help?

[dibog]

Hi @oleksiyp, I have the same issue with inline classes as return value of a mockk call:

every { somthing} return InstanceId("value")

The Issue #152 seems to addresses inline classes as parameter but not as return value.

[angryziber]

3 years in the making... Unfortunately, mockk's own code is very complex, not easy to contribute...