在open(file)中模拟行: [英] Mock for line in open(file):

问题描述

我想对应用程序的组件进行单元测试.该代码如下所示.

I am wanting to unittest a component of my application. The code looks a little like below.

def read_content_generator(myfile):
    for line in open(myfile):
        # do some string manipulation.
        yield result

我遇到的问题是我无法在for循环中模拟open()功能.

The problem I am having is that I cannot mock the open() functionality within a for loop.

我想要的是这样的unittest :(我知道这段代码不正确，但这只是我要执行的操作的一个示例):

What I am aiming for is a unittest like this: (I know this code is not right but its just an example of what I am trying to do):

def test_openiteration(self):
    with mock.patch('open') as my_openmock:
        my_openmock.return_value = ['1','2','3']
        response = myfunction()
        self.assertEquals([1,2,3], response)

推荐答案

您可以模拟open()返回StringIO对象.

You can mock open() to return StringIO object.

mymodule.py:

def read_content_generator(myfile):
    with open(myfile) as f:
        for line in f:
            yield '<{}>'.format(line)

请注意，我在此处使用了带有语句.

Note that I've used with statement there.

test_mymodule.py:

import io
import unittest
import unittest.mock as mock

import mymodule


class Tests(unittest.TestCase):
    def test_gen(self):
        fake_file = io.StringIO('foo\nbar\n')
        with mock.patch('mymodule.open', return_value=fake_file, create=True):
            result = list(mymodule.read_content_generator('filename'))
        self.assertEqual(result, ['<foo\n>' , '<bar\n>'])

适用于python3.4.

Works for python3.4.

起初我尝试使用mock.mock_open(read_data='1\n2\n3\n')，但是对迭代的支持似乎被破坏了.

At first I tried to use mock.mock_open(read_data='1\n2\n3\n') but iteration support seems to be broken.

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