How can one mock/stub python module like urllib

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Another simple approach is to have your test override urllib’s urlopen() function. For example, if your module has

import urllib

def some_function_that_uses_urllib():
    ...
    urllib.urlopen()
    ...

You could define your test like this:

import mymodule

def dummy_urlopen(url):
    ...

mymodule.urllib.urlopen = dummy_urlopen

Then, when your tests invoke functions in mymodule, dummy_urlopen() will be called instead of the real urlopen(). Dynamic languages like Python make it super easy to stub out methods and classes for testing.

See my blog posts at http://softwarecorner.wordpress.com/ for more information about stubbing out dependencies for tests.

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