Class cast exception while mocking MutableList about mockk HOT 3 CLOSED

public fun <T> Iterable<T>.toList(): List<T> {
    if (this is Collection) {
        return when (size) {
            0 -> emptyList()
            1 -> listOf(if (this is List) get(0) else iterator().next())
            else -> this.toMutableList()
        }
    }
    return this.toMutableList().optimizeReadOnlyList()
}

    val mutableList = mockk<MutableList<String>>()

    @Test
    fun test() {
        every { mutableList.size } returns 1
        every { mutableList.get(0) } returns "1"

        val list = mutableList.toList()
        assertEquals(listOf("1"), list)
    }