Issue 33236: MagicMock().iter.return_value is different from MagicMock().iter() (original) (raw)

Created on 2018-04-06 11:50 by mrh1997, last changed 2022-04-11 14:58 by admin. This issue is now closed.

Messages (5)
msg315016 - (view)	Author: Robert (mrh1997) *	Date: 2018-04-06 11:50
According to the documentation .return_value should be identical to the object returned when calling the mock ("assert m() is m.return_value") This is the case except on objects returned by __iter__ on MagicMocks. The following script demonstrates the problem: ---- from unittest.mock import MagicMock m = MagicMock() assert x.__iter__() is x.__iter__.return_value # <- fails ---- In fact __iter__() returns the object "iter([])" (which matches the documentation) while __iter__.return_value return a MagicMock object (which does not match the documentation). When replacing "__iter__" with any other special function MagicMock works as expected.
msg325863 - (view)	Author: Karthikeyan Singaravelan (xtreak) *	Date: 2018-09-20 12:37
Can you please link to the relevant documentation that is misleading? As I can see from the source code return value is a Mock object [1] which I believe the docs state as below : https://docs.python.org/3/library/unittest.mock.html#calling > Mock objects are callable. The call will return the value set as the return_value attribute. The default return value is a new Mock object; it is created the first time the return value is accessed (either explicitly or by calling the Mock) - but it is stored and the same one returned each time. from unittest.mock import MagicMock x = MagicMock() print(x.__iter__()) print(x.__iter__.return_value) print(x.return_value) ➜ cpython git:(master) ./python.exe bpo33236.py <list_iterator object at 0x10d0797f0> [1] : https://github.com/python/cpython/blob/b10a64d117de6121ea3e79c467c4107f8f399f3d/Lib/unittest/mock.py#L463 Thanks
msg325927 - (view)	Author: Robert (mrh1997) *	Date: 2018-09-20 20:31
According to this chapter ( https://docs.python.org/3/library/unittest.mock.html#unittest.mock.MagicMock ) the specialmethods in MagicMock are different: .return_value is preinitialized with defaultvalues, which depends on the operator. In the case of .__iter__ this is "iter([])". This is the case when running __iter__(), but not when running __iter__.result_value
msg328649 - (view)	Author: Mario Corchero (mariocj89) *	Date: 2018-10-27 13:52
iter is initialized by using side_effects, not return_value. The statement "According to the documentation .return_value should be identical to the object returned when calling the mock" works only when it return_value has been used to define the behaviour of the mock. Example: ``` >>> m = MagicMock(side_effect=lambda: 1) >>> m() 1 >>> m.return_value >>> m() is m.return_value False ```
msg328652 - (view)	Author: Michael Foord (michael.foord) *	Date: 2018-10-27 15:41
This isn't a bug. This is the intended behaviour, otherwise MagicMock objects would error out on iteration.