Python 用补丁模拟两个函数进行单元测试
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Mocking two functions with patch for a unit test
提问by cnodell
I have a function I want to unit test contains calls two other functions. I am unsure how can I mock both functions at the same time properly using patch. I have provided an example of what I mean below. When I run nosetests, the tests pass but I feel that there must be a cleaner way to do this and I do not really Understand the piece regarding f.close()...
我有一个函数我想单元测试包含调用另外两个函数。我不确定如何正确使用补丁同时模拟这两个函数。我在下面提供了一个例子来说明我的意思。当我运行鼻子测试时，测试通过了，但我觉得必须有一种更简洁的方法来做到这一点，而且我并不真正理解关于 f.close() 的部分......
The directory structure looks like this:
目录结构如下所示：
program/
program/
data.py
tests/
data_test.py
data.py:
数据.py：
import cPickle
def write_out(file_path, data):
f = open(file_path, 'wb')
cPickle.dump(data, f)
f.close()
data_test.py:
数据测试.py：
from mock import MagicMock, patch
def test_write_out():
path = '~/collection'
mock_open = MagicMock()
mock_pickle = MagicMock()
f_mock = MagicMock()
with patch('__builtin__.open', mock_open):
f = mock_open.return_value
f.method.return_value = path
with patch('cPickle.dump', mock_pickle):
write_out(path, 'data')
mock_open.assert_called_once_with('~/collection', 'wb')
f.close.assert_any_call()
mock_pickle.assert_called_once_with('data', f)
Results:
结果：
$ nosetests
.
----------------------------------------------------------------------
Ran 1 test in 0.008s
OK
采纳答案by Matti John
You can simplify your test by using the patch decorator and nesting them like so (they are MagicMockobjects by default):
您可以通过使用补丁装饰器并像这样嵌套它们来简化测试（MagicMock默认情况下它们是对象）：
@patch('cPickle.dump')
@patch('__builtin__.open')
def test_write_out(mock_open, mock_pickle):
path = '~/collection'
f = mock_open.return_value
f.method.return_value = path
write_out(path, 'data')
mock_open.assert_called_once_with('~/collection', 'wb')
mock_pickle.assert_called_once_with('data', f)
f.close.assert_any_call()
Calls to a MagicMockinstance return a new MagicMockinstance, so you can check that the returned value was called just like any other mocked object. In this case fis a MagicMocknamed 'open()'(try printing f).
调用MagicMock实例会返回一个新MagicMock实例，因此您可以像调用任何其他模拟对象一样检查返回值是否被调用。在这种情况下f是一个MagicMock命名'open()'（尝试打印f）。
回答by alecxe
Here's a simple example on how to test raising ConflictErrorin create_collectionfunction using mock:
这是一个关于如何使用模拟ConflictError在create_collection函数中测试提升的简单示例：
import os
from unittest import TestCase
from mock import patch
from ..program.data import ConflictError, create_collection
class TestCreateCollection(TestCase):
def test_path_exists(self):
with patch.object(os.path, 'exists') as mock_method:
mock_method.return_value = True
self.assertRaises(ConflictError, create_collection, 'test')
Please, also see mock docsand Michael Foord's awesome introduction to mock.
回答by Alex Lisovoy
In addition to the response @Matti John you can also use patchinside function test_write_out:
除了响应@Matti John 您还可以使用patch内部函数test_write_out：
from mock import MagicMock, patch
def test_write_out():
path = '~/collection'
with patch('__builtin__.open') as mock_open, \
patch('cPickle.dump') as mock_pickle:
f = mock_open.return_value
...
