python-3.x - python : How do I mock an async method that gets called multiple times?

Question

我有一种用于在 Python (3.6) 中测试异步代码的方法:

@asyncio.coroutine
def coroutine_creater(value):
    return value

我像这样使用它:

async def test_test():
    my_mock = Mock(return_value=coroutine_creater(5))

    # I call with "await"
    first_call = await my_mock()
    second_call = await my_mock()

    assert first_call == 5, 'first call failed'
    assert second_call == 5, 'second call failed'  # this call fails

这样我就可以为异步调用创建模拟。我发现如果我调用 async 方法两次，这将不起作用。在我的代码中， first_call像我期望的那样等于 5，但是 second_call等于无。这里发生了什么？如何测试多次调用 Mock 异步方法的代码？

Answer 1

您应该设置 side_effect Mock 的论据.

side_effect: A function to be called whenever the Mock is called. See the side_effect attribute. Useful for raising exceptions or dynamically changing return values. The function is called with the same arguments as the mock, and unless it returns DEFAULT, the return value of this function is used as the return value.

下面的示例使用 pytest-asyncio和 pytest模块: code_53856568.py :

import asyncio


@asyncio.coroutine
def coroutine_creater(value):
    return value

test_code_53856568.py :

from unittest.mock import Mock
from code_53856568 import coroutine_creater
import pytest


@pytest.mark.asyncio
async def test_test():
    def coroutine_creater_side_effect():
        return coroutine_creater(5)

    my_mock = Mock(side_effect=coroutine_creater_side_effect)

    first_call = await my_mock()
    second_call = await my_mock()

    assert first_call == 5, 'first call failed'
    assert second_call == 5, 'second call failed'

带有覆盖率报告的单元测试结果:

(venv) ☁  python-codelab [master] ⚡  coverage run -m pytest /Users/ldu020/workspace/github.com/mrdulin/python-codelab/src/stackoverflow/53856568/test_code_53856568.py && coverage report -m --include="src/*"
===================================================================================================================== test session starts =====================================================================================================================
platform darwin -- Python 3.7.5, pytest-5.3.1, py-1.8.0, pluggy-0.13.1
rootdir: /Users/ldu020/workspace/github.com/mrdulin/python-codelab
plugins: asyncio-0.10.0
collected 1 item                                                                                                                                                                                                                                              

src/stackoverflow/53856568/test_code_53856568.py .                                                                                                                                                                                                      [100%]

====================================================================================================================== 1 passed in 0.04s ======================================================================================================================
Name                                               Stmts   Miss  Cover   Missing
--------------------------------------------------------------------------------
src/stackoverflow/53856568/code_53856568.py            3      0   100%
src/stackoverflow/53856568/test_code_53856568.py      11      0   100%
--------------------------------------------------------------------------------
TOTAL