[英]How to check if a function was called in a unit test using pytest-mock?
I have a unit test where I want to check if a function was called.我有一个单元测试,我想检查一个函数是否被调用。 How do I do this with
pytest
and pytest-mock
libraries?如何使用
pytest
和pytest-mock
库执行此操作?
For example, here is a unit test test_hello.py
.例如,这是一个单元测试
test_hello.py
。 In this test I call the function my_function
and want to verify that it called hello
with a given argument.在这个测试中,我调用函数
my_function
并想验证它是否使用给定的参数调用了hello
。
def hello(name):
return f'Hello {name}'
def my_function():
hello('Sam')
def test_hello(mocker):
mocker.patch('hello')
my_function()
hello.assert_called_once_with('Sam')
The code above returns the following error:上面的代码返回以下错误:
target = 'hello'
def _get_target(target):
try:
> target, attribute = target.rsplit('.', 1)
E ValueError: not enough values to unpack (expected 2, got 1)
/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/unittest/mock.py:1393: ValueError
During handling of the above exception, another exception occurred:
mocker = <pytest_mock.MockFixture object at 0x109c5e978>
def test_hello(mocker):
> mocker.patch('hello')
test_hello.py:8:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/pytest_mock.py:156: in __call__
return self._start_patch(self.mock_module.patch, *args, **kwargs)
/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/pytest_mock.py:134: in _start_patch
p = mock_func(*args, **kwargs)
/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/unittest/mock.py:1544: in patch
getter, attribute = _get_target(target)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
target = 'hello'
def _get_target(target):
try:
target, attribute = target.rsplit('.', 1)
except (TypeError, ValueError):
raise TypeError("Need a valid target to patch. You supplied: %r" %
> (target,))
E TypeError: Need a valid target to patch. You supplied: 'hello'
/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/unittest/mock.py:1396: TypeError
Solving the error by 通过解决错误
assign a mocked_hello
to mocked.patch
将
mocked_hello
分配给mocked.patch
assign a side_effect
to mocked func 为mocked func分配
side_effect
def bonjour(name):
return 'bonjour {}'.format(name)
def hello(name):
return 'Hello {}'.format(name)
def my_function():
return hello('Sam')
def test_hellow_differnt_from_module(mocker):
# mocked func with `test_hello.py` as module name
mocked_hello = mocker.patch('test_hello.hello')
# assign side_effect to mocked func
mocked_hello.side_effect = bonjour
# the mocked func return_value changed by side_effect
assert mocked_hello('Sam') == 'bonjour Sam'
# the mocked func called with Sam, but with different return value
mocked_hello.assert_called_with('Sam')
call a real function my_function() and the verify that it called hello
调用一个真正的函数my_function()并验证它是否调用了hello
def test_my_function(mocker):
mocker.patch('test_hello.hello', side_effect=bonjour)
mf = my_function()
hello.assert_called_with('Sam')
assert mf == 'bonjour Sam'
I think the minimal change to the OP's code that would make it work would be simply to fully qualify the name of the mocked function.我认为对 OP 代码进行的最小更改将使其工作只是完全限定模拟函数的名称。 So, for example, if the code is in a file called
test.py
:因此,例如,如果代码位于名为
test.py
的文件中:
import pytest
def hello(name):
return f'Hello {name}'
def my_function():
hello('Sam')
def test_hello(mocker):
mocker.patch('test.hello')
my_function()
hello.assert_called_once_with('Sam')
(I'm assuming test.py
is located somewhere in sys.path
.) (我假设
test.py
位于sys.path
某处。)
However, I think it's better to change the test function to be:但是,我认为最好将测试功能更改为:
def test_hello(mocker):
mocked_func = mocker.patch('test.hello')
my_function()
mocked_func.assert_called_once_with('Sam')
That form seems clearer to me and is less likely to raise an AttributeError in more complex code.这种形式对我来说似乎更清晰,并且不太可能在更复杂的代码中引发 AttributeError 。
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