Mocking python function based on input arguments
If
side_effect_funcis a function then whatever that function returns iswhat calls to the mock return. Theside_effect_funcfunction is called withthe same arguments as the mock. This allows you to vary the returnvalue of the call dynamically, based on the input:>>> def side_effect_func(value):... return value + 1...>>> m = MagicMock(side_effect=side_effect_func)>>> m(1)2>>> m(2)3>>> m.mock_calls[call(1), call(2)]
As indicated at Python Mock object with method called multiple times
A solution is to write my own side_effect
def my_side_effect(*args, **kwargs): if args[0] == 42: return "Called with 42" elif args[0] == 43: return "Called with 43" elif kwargs['foo'] == 7: return "Foo is seven"mockobj.mockmethod.side_effect = my_side_effectThat does the trick
Side effect takes a function (which can also be a lambda function), so for simple cases you may use:
m = MagicMock(side_effect=(lambda x: x+1))