In Kotlin, when mocking objects with suspend member functions (ie coroutine methods), setting up test expectations for those suspend functions can be a bit cumbersome when they have matcher arguments:

interface TestSusp {
    suspend fun testWithArg(s: String?): String
    suspend fun testWithoutArg(): String
}

class TestSuspTest {
    @Test
    fun mockTest() = runBlocking {
        val t = EasyMock.mock<TestSusp>(TestSusp::class.java)
        EasyMock.expect(
            t.testWithArg(
                Pair(EasyMock.anyString(), EasyMock.anyObject<Continuation<*>>()).first
            )
        )
            .andReturn("abc")
        EasyMock.expect(t.testWithoutArg()).andReturn("def")
        EasyMock.replay(t)
        Assert.assertEquals(t.testWithArg("a"), "abc")
        Assert.assertEquals(t.testWithoutArg(), "def")
        EasyMock.verify(t)
    }
}

Trying the naive EasyMock.expect(t.testWithArg(EasyMock.anyString())).andReturn("abc") results in: java.lang.IllegalStateException: 2 matchers expected, 1 recorded.It does work with value expectations:EasyMock.expect(t.testWithArg("a")).andReturn("abc"), and with no-arg functions for the same reason (I assume it"s matching a compiler inserted continuation value).

Not sure if there"s a way to implement some way to automatically include a Continuation matcher as the last argument for suspend functions (or if there"d only be a way to do so by adding potentially unwanted kotlin dependencies?)?