[TIP] Using Mock to patch an iterator / generator?
michael at voidspace.org.uk
Mon Jun 13 07:57:03 PDT 2011
On 11/06/2011 10:35, Michael Foord wrote:
> On 10/06/2011 00:08, Andrew Hammond wrote:
>> I have a class that looks like
>> class Foo(object):
>> def iter(descending=False):
>> for r in something_iterable:
>> yield r
> Hey Andrew,
> Because of the use of yield, your iter is a generator and not a normal
> method. Mocking a generator (or any iterable) can be done with the
> MagicMock (in mock 0.7).
> You can then configure the return values using something similar to this:
> mock = MagicMock()
> values = [1, 2, 3]
> mock.iter.__iter__.side_effect = lambda: values.pop()
Actually, this isn't quite correct (my apologies).
Foo.iter *returns* a generator when called. It isn't directly a
generator. Also the __iter__ method should return the iterator.
>>> values = [1, 2, 3]
>>> mock_foo = MagicMock()
>>> mock_foo.iter.return_value.__iter__.return_value = iter(values)
[1, 2, 3]
I'm adding this as a recipe to the "examples" page as I got it wrong on
the first attempt... :-)
> All the best,
> Michael Foord
>> I would like to mock the class and patch Foo.iter. I have tried a
>> number of things without luck.
>> class TestFoo(PatchedTestCase):
>> _partitions = 
>> def partitions(self):
>> for p in self._partitions:
>> yield p
>> def postSetUpPreRun(self):
>> self._partitions = [ 1, 2, 3, 4 ]
>> rw = Mock(spec=Foo)
>> self.mock_RollingWindow = rw
>> rw.iter = Mock()
>> rw.iter.side_effect = self.partitions
>> This is following the pattern I've used for other methods, but
>> doesn't work for an iterator... so, what is the proper approach please?
>> testing-in-python mailing list
>> testing-in-python at lists.idyll.org
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> -- the sqlite blessinghttp://www.sqlite.org/different.html
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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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