Mocking unsigned Kotlin types ends in java.lang.ClassCastException

[bio007]

I'm mocking simple function returning UInt but after that method is executed in the test it crashes with java.lang.ClassCastException.

every { calculator.compute(any()) } returns 23859762u

Expected Behavior

No crash, mocked function returns unsigned number result.

Current Behavior

Exception java.lang.ClassCastException: kotlin.UInt cannot be cast to java.lang.Integer is thrown in case of UInt return type.

Steps to Reproduce

1. Write mockk every function for a method returning unsigned number like UInt
2. Call this function in the test
3. Exception is thrown

Context

• MockK version: 1.10.0
• OS: macOS Catalina
• Kotlin version: 1.3.72
• JUnit version: 4.12
• Type of test: unit test

Minimal reproducible code (the gist of this issue)

    every { calculator.compute(any()) } returns 23859762u
    assertEquals(23859762u, calculator.compute(42))

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[d35h]

Looks like something not related to mockk itself as mockk calls byte-buddy under the hood and then byte-buddy delegates getting declaration of methods to Class from jdk: ByteBuddy::MethodList::type::getDeclaredMethods, which returns int instead of UInt. I'd say that Kotlin's UInt is not interpolated correctly by this method making UInt as Int

[ianbrandt]

I ran into what may be the same issue trying to verify behavior on a mock with a method that takes a UShortArray:

interface MyInterface {
    suspend fun myMethod(arg1: UShortArray, arg2: Int, arg3: Int)
}

runBlockingTest {

    val mockMyInterface = mockk<MyInterface>()
    ...
    coVerify {
        mockMyInterface.myMethod(any(), any(), any())
    }
}

The error refers to trying to match a signature with ShortArray instead of UShortArray:

Failed matching mocking signature for
SignedCall(retValue=, isRetValueMock=true, retType=class kotlin.Any, self=MyInterface(#1), method=myMethod-GWzLcNs(ShortArray, Int, Int, Continuation), args=[null, 866937822, -1738456294, Continuation at my.package.MyTest$test my method$1$1.invokeSuspend(MyTest.kt:10)], invocationStr=MyInterface(#1).myMethod-GWzLcNs(null, 866937822, -1738456294, continuation {}))
left matchers: [any()]

[Raibaz]

Unsigned integer support in Kotlin is still in beta, so I guess @d35h is right.

[Kantis]

I guess #633 might resolve this, since unsigned types are implemented using value classes

[nosideeffects]

Does not look like #633 solved this issue. Any idea the scope of work to get this to work?

[migueltorcha]

Same issue here trying to mock a UByte:

interface MyInterface {
  suspend fun myMethod(): UByte?
}

....

coEvery { myInterface.myMethod() } returns Random.nextInt().toUByte()

As result, I have the next:
class java.lang.Byte cannot be cast to class kotlin.UByte (java.lang.Byte is in module java.base of loader 'bootstrap'; kotlin.UByte is in unnamed module of loader 'app') java.lang.ClassCastException: class java.lang.Byte cannot be cast to class kotlin.UByte (java.lang.Byte is in module java.base of loader 'bootstrap'; kotlin.UByte is in unnamed module of loader 'app')

[cdprete]

I do have the same issue even with version 1.12.5 on a @RelaxedMockK with a UInt nullable field.

[cdprete]

I can confirm the same issue is present even with version 1.13.3 and Kotlin 1.8

[zTrap]

Problem still here. mockk 1.13.8, kotlin 1.9.10

[brian-livefront]

This issue still seems to be present on 1.13.10. See #1226