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Python:如何模拟多次调用的异步方法?

python-asyncio mocking python-3.x

user2023861 · 技术社区 · 7 年前

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

我是这样用的:

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,这就行不通了。在我的密码里, first_call 像我预期的那样等于5,但是 second_call 等于无。这是怎么回事?如何测试多次调用模拟异步方法的代码?

0 回复 | 直到 7 年前

Lin Du Correcter 5 年前

你应该设置 side_effect Mock

side_effect:每当调用Mock时都要调用的函数。请参见“副作用”属性。用于引发异常或动态更改返回值。使用与mock相同的参数调用函数,除非它返回DEFAULT,否则将使用此函数的返回值作为返回值。

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'

单元测试结果和覆盖率报告:

(venv) â  python-codelab [master] â¡  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