async def METHOD_NAME(opcode):
    assembler = WebsocketFrameAssembler(Mock())
    assembler.message_fetched = AsyncMock()
    assembler.message_fetched.is_set = Mock(return_value=False)
    await assembler.put(Frame(opcode, b""))
    assembler.message_fetched.wait.assert_awaited_once()
    assembler.message_fetched.clear.assert_called_once()