[TIP] Return different values based on an argument passed to a method
michael at voidspace.org.uk
Mon Mar 5 04:41:57 PST 2012
On 05/03/2012 12:33, Marcin Zajączkowski wrote:
> Is it possible to simple stub a method's return value when called with an argument (any argument or specific one)?
> I tried with:
> mock = Mock()
> but in a debugger I see that in my code mock.foo(<<some_object>>) returns a mock instead of False value. If not the returning value I could use assert_called_with with custom mather, but how to return different value based on an argument?
To change the return value of mock.foo you set mock.foo.return_value.
mock.foo(ANY).return_value(False) is fetching the return_value mock got
by calling mock.foo - and then calling that mock with False! (You're not
setting any return_value at all, you're just making calls.)
To have mock.foo return False, do this:
mock.foo.return_value = False
It's not entirely clear to me from your post, but if you want to you can
dynamically change the value returned from a call using side_effect.
>>> from mock import MagicMock
>>> def side_effect(arg):
... if arg == 1:
... return False
... return True
>>> m = MagicMock()
>>> m.foo.side_effect = side_effect
All the best,
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