Jim Jeon added the comment:
Thank you all for the kind answers.
I didn't know copying could cause so many problems.
@veky
Thank you for the example.
But it seems that the example will actually raise and I think it should.
I am talking f.assert_called_with(b) when `b` has same values
New submission from Jim Jeon :
When `assert_called_with` is used with mutable object, test fails if the object
has changed. I think this is not what it meant to do.
https://docs.python.org/dev/library/unittest.mock-examples.html#coping-with-mutable-arguments
The same situation is explained
