NoSuchElementException in verify()

[mmimica]

I'm calling a verify(timeout = 3_000, exactly = 3) { mock.offer(any()) }
and I'm getting:

java.util.NoSuchElementException: List is empty.
	at kotlin.collections.CollectionsKt___CollectionsKt.first(_Collections.kt:214)
	at io.mockk.impl.verify.UnorderedCallVerifier.matchCall(UnorderedCallVerifier.kt:110)
	at io.mockk.impl.verify.UnorderedCallVerifier.verify(UnorderedCallVerifier.kt:40)
	at io.mockk.impl.verify.TimeoutVerifier.verify(TimeoutVerifier.kt:22)
	at io.mockk.impl.recording.states.VerifyingState$recordingDone$outcome$1.invoke(VerifyingState.kt:31)
	at io.mockk.impl.recording.states.VerifyingState$recordingDone$outcome$1.invoke(VerifyingState.kt:30)
	at io.mockk.impl.recording.CommonCallRecorder.safeExec(CommonCallRecorder.kt:72)
	at io.mockk.impl.recording.states.VerifyingState.recordingDone(VerifyingState.kt:30)
	at io.mockk.impl.recording.CommonCallRecorder.done(CommonCallRecorder.kt:47)
	at io.mockk.impl.eval.RecordedBlockEvaluator.record(RecordedBlockEvaluator.kt:63)
	at io.mockk.impl.eval.VerifyBlockEvaluator.verify(VerifyBlockEvaluator.kt:30)
	at io.mockk.MockKDsl.internalVerify(API.kt:120)
	at io.mockk.MockKKt.verify(MockK.kt:218)
	at io.mockk.MockKKt.verify$default(MockK.kt:209)

Method signature is @NotNull Resp offer(@NotNull Req req) and it is mocked with

val capture = CopyOnWriteArrayList<Req>()
mock.apply {
                    every { offer(capture(capture)) } answers {
                        ...
                        Resp()
                    }

Nothing special IMO. I can't reproduce it but hope the above helps.

• MockK version: 1.13.9
• OS: Linux
• Kotlin version: 1.9.21
• JDK version: 17

[Raibaz]

Why are you using CopyOnWriteArrayList for argument capturing?

capture supports slot and MutableList, I don't think it works with CopyOnWriteArrayList.

[mmimica]

CopyOnWriteArrayList is a MutableList.

[mmimica]

And I use it because the mock is invoked from different threads concurrently. The capturing list must be thread-safe.