我需要测试一个函数，该函数需要使用urllib.urlopen（它也使用urllib.urlencode）来查询外部服务器上的页面。服务器可能已关闭，页面可能已更改；我不能依靠它进行测试。
控制urllib.urlopen返回的最佳方法是什么？
Answers:
另一个简单的方法是让您的测试覆盖urllib的urlopen()功能。例如，如果您的模块具有
import urllib
def some_function_that_uses_urllib():
...
urllib.urlopen()
...
您可以这样定义测试：
import mymodule
def dummy_urlopen(url):
...
mymodule.urllib.urlopen = dummy_urlopen
然后，当您的测试调用中的函数时mymodule，dummy_urlopen()将调用而不是real urlopen()。像Python这样的动态语言，使测试方法和类的存根非常容易。
请参阅我的博客文章，网址为http://softwarecorner.wordpress.com/，以获取有关测试依赖项的更多信息。
我正在使用Mock的补丁装饰器：
from mock import patch
[...]
@patch('urllib.urlopen')
def test_foo(self, urlopen_mock):
urlopen_mock.return_value = MyUrlOpenMock()
你给莫克斯看了吗？它应该做您需要的一切。这是一个简单的交互式会话，说明您需要的解决方案：
>>> import urllib
>>> # check that it works
>>> urllib.urlopen('http://www.google.com/')
<addinfourl at 3082723820L ...>
>>> # check what happens when it doesn't
>>> urllib.urlopen('http://hopefully.doesnotexist.com/')
#-- snip --
IOError: [Errno socket error] (-2, 'Name or service not known')
>>> # OK, let's mock it up
>>> import mox
>>> m = mox.Mox()
>>> m.StubOutWithMock(urllib, 'urlopen')
>>> # We can be verbose if we want to :)
>>> urllib.urlopen(mox.IgnoreArg()).AndRaise(
... IOError('socket error', (-2, 'Name or service not known')))
>>> # Let's check if it works
>>> m.ReplayAll()
>>> urllib.urlopen('http://www.google.com/')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python2.5/site-packages/mox.py", line 568, in __call__
raise expected_method._exception
IOError: [Errno socket error] (-2, 'Name or service not known')
>>> # yay! now unset everything
>>> m.UnsetStubs()
>>> m.VerifyAll()
>>> # and check that it still works
>>> urllib.urlopen('http://www.google.com/')
<addinfourl at 3076773548L ...>
HTTPretty的工作方式与FakeWeb完全相同。HTTPretty在套接字层工作，因此它应能拦截任何python http客户端库。经过针对urllib2，httplib2和请求的测试
import urllib2
from httpretty import HTTPretty, httprettified
@httprettified
def test_one():
HTTPretty.register_uri(HTTPretty.GET, "http://yipit.com/",
body="Find the best daily deals")
fd = urllib2.urlopen('http://yipit.com')
got = fd.read()
fd.close()
assert got == "Find the best daily deals"
如果您甚至不想加载模块：
import sys,types
class MockCallable():
""" Mocks a function, can be enquired on how many calls it received """
def __init__(self, result):
self.result = result
self._calls = []
def __call__(self, *arguments):
"""Mock callable"""
self._calls.append(arguments)
return self.result
def called(self):
"""docstring for called"""
return self._calls
class StubModule(types.ModuleType, object):
""" Uses a stub instead of loading libraries """
def __init__(self, moduleName):
self.__name__ = moduleName
sys.modules[moduleName] = self
def __repr__(self):
name = self.__name__
mocks = ', '.join(set(dir(self)) - set(['__name__']))
return "<StubModule: %(name)s; mocks: %(mocks)s>" % locals()
class StubObject(object):
pass
接着：
>>> urllib = StubModule("urllib")
>>> import urllib # won't actually load urllib
>>> urls.urlopen = MockCallable(StubObject())
>>> example = urllib.urlopen('http://example.com')
>>> example.read = MockCallable('foo')
>>> print(example.read())
'foo'
处理此问题的最佳方法可能是拆分代码，以便将处理页面内容的逻辑与获取页面的代码分开。
然后将获取程序代码的实例传递到处理逻辑中，然后可以轻松地用模拟获取程序替换它以进行单元测试。
例如
class Processor(oject):
def __init__(self, fetcher):
self.m_fetcher = fetcher
def doProcessing(self):
## use self.m_fetcher to get page contents
class RealFetcher(object):
def fetchPage(self, url):
## get real contents
class FakeFetcher(object):
def fetchPage(self, url):
## Return whatever fake contents are required for this test
最简单的方法是更改函数，使其不必使用urllib.urlopen。假设这是您的原始功能：
def my_grabber(arg1, arg2, arg3):
# .. do some stuff ..
url = make_url_somehow()
data = urllib.urlopen(url)
# .. do something with data ..
return answer
添加一个参数，该参数是用于打开URL的函数。然后，您可以提供一个模拟函数来执行所需的任何操作：
def my_grabber(arg1, arg2, arg3, urlopen=urllib.urlopen):
# .. do some stuff ..
url = make_url_somehow()
data = urlopen(url)
# .. do something with data ..
return answer
def test_my_grabber():
my_grabber(arg1, arg2, arg3, urlopen=my_mock_open)
requests：如何模拟请求和响应？