Mockito 5.0 breaks vararg argument capture in Kotlin

[emartynov]

Hence issue was wrongly put on the mockito project.

Have code:

class PreferencesRepository {
    suspend fun getPreferences(
        vararg preferences: String
    ): Map<String, Any> 
{}

Write tests:

        val preferencesRepository: PreferencesRepository = mock()
        val preferencesCapture = argumentCaptor<String>()
        whenever(preferencesRepository.getPreferences(anyVararg())) doReturn emptyMap()

        verify(preferencesRepository).getPreferences(preferencesCapture.capture())

Run test and observe:

at PreferencesRepository.getPreferences(PreferecesRepository.kt:11)
Actual invocations have different arguments:
preferencesRepository.getPreferences(
    [String, String]
);

[emartynov]

Moved from mockito/mockito#2878

[TimvdLippe]

If anybody would like to stab at this, I am happy to review a PR with a regression test + fix.

[kschults]

I see that the PR 2807 got merged, which looks like it's trying to fix this. Any estimate on when this will be available?

[TimvdLippe]

@kschults I think 2807 is the PR that introduced the problems for Kotlin (while it works fine for Java).

[kschults]

Oh, I see, I misread the timeline. Thanks.

[samabcde]

Come up with this workaround. Honestly speaking, I don't really understand why it works.

inline fun <reified T : Any, reified E : Any> anyVararg(clazz: KClass<E>): T {
    return ArgumentMatchers.any(T::class.java)
          ?: arrayOf(createInstance(E::class)) as T
}

// below methods are from org/mockito/kotlin/internal/CreateInstance.kt
fun <T : Any> createInstance(kClass: KClass<T>): T {
    return castNull()
}
@Suppress("UNCHECKED_CAST")
private fun <T> castNull(): T = null as T

    @Test
    fun testVararg() {
        val preferencesRepository: PreferencesRepository = mock()
        val preferencesCapture = argumentCaptor<String>()
        // not the * before anyVararg
        whenever(preferencesRepository.getPreferences(*anyVararg(String::class))) doReturn emptyMap()
        preferencesRepository.getPreferences("works!")
        verify(preferencesRepository).getPreferences(preferencesCapture.capture())
        assert(preferencesCapture.lastValue == "works!")
    }

[lukas-krecan]

This might help https://github.com/mockito/mockito-kotlin/pull/482/files#diff-1354c4c5b4595d316a42f5172d59654a6d90a1516f7b8ee0fd116ef45c3d3eb3R62