[TIP] Patching __import__

[Yoni Tsafir]

Yep that one works well.
I'll use it for now :)

Actually I use patch.dict("...").start() in setUp and .stop() at tearDown,
but it's the same concept...

Would like to debug nose but a bit on a deadline with this task so I'll have
to postpone it.


On Wed, May 25, 2011 at 2:06 AM, Michael Foord <michael at voidspace.org.uk>wrote:

>  On 24/05/2011 08:31, Yoni Tsafir wrote:
>
> Moving a discussion with Michael Foord to TIP so everyone can contribute:
>
>  I suggested a feature to the mock framework in which you can mock non
> existing imports (useful when you are unit-testing platform dependent code).
>
>  My solution for this was the following:
>
>  real_import = __import__
>
>  def windows_safe_import(name, globals={}, locals={}, fromlist=(), *args,
> **kargs):
>     if name in ["wmi", "win32api"] or (name == "ctypes" and fromlist is not
> None and "windll" in fromlist):
>         return MagicMock()
>
>     else:
>         return real_import(name, globals, locals, fromlist, *args, **kargs)
>
>  @patch("__builtin__.__import__", new = windows_safe_import)
> class MyTestCase(unittest.TestCase):
>  ...
>  # (tested module was imported only inside the test so the problematic
> imports it uses won't be imported before we mock the __import__)
>
>  Michael suggested 2 alternatives:
>  1.
>     import sys
>     sys.modules['wmi'] = MagicMock()
>
>  2.
>     @patch.dict('sys.modules', {'wmi': MagicMock()})
>
>  Then "import wmi" will find your mock. I'm very wary of
> overriding __import__ even in tests.
>
>  Well, just wanted to update that #1 works well, but #2 causes something
> weird:
> On PyDev I can run the tests fine, but when I try running them with
> nosetests, nose doesn't recognize any tests. If I comment out the
> @patch.dict line, everything works fine.
> Tried to debug it a bit but no luck...
>
>
> Note that one fix *may* be (if you're using Python 2.5 or more recent) to
> use patch.dict as a context manager so that it is called inside the test
> instead of at test import time:
>
>     def test_something():
>         with patch.dict('sys.modules', {'wmi': MagicMock()}):
>             ...
>
> All the best,
>
> Michael
>
>
>   Any ideas?
>
>
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>
>
> --
> http://www.voidspace.org.uk/
>
> May you do good and not evil
> May you find forgiveness for yourself and forgive others
> May you share freely, never taking more than you give.
> -- the sqlite blessing http://www.sqlite.org/different.html
>
>
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