[FIXED] How to mock a dictionary in Python

Issue

Let's say I have a function like this:

def do_something(dict_obj):
   # access to the dict_obj then do some stuff
   eg.
   if dict_obj['doors']:
      do_something_with_doors()
   map_car_make(dict_obj['make'])
   ...

   if dict_obj['is_active']:
        do_something_else()

I want to mock the dict_obj to have is_active element and don't care the rest, how do I do that?

Solution

How to mock a dictionary in Python is a good/direct question someone else can search, so:

1. I suggest MagicMock instead of Mock
2. Overload the __getitem__

from unittest.mock import MagicMock

m = MagicMock()
d = {'key_1': 'value'}
m.__getitem__.side_effect = d.__getitem__

# dict behaviour
m['key_1'] # => 'value'
m['key_2'] # => raise KeyError

# mock behaviour
m.foo(42)
m.foo.assert_called_once_with(43) # => raise AssertionError

Related Questions:

• How to let MagicMock behave like a dict?
• Understanding __getitem__ method

=== EDIT ===

As a function for direct copy/pasting

def mock_dict(d):
  m = MagicMock()
  m.__getitem__.side_effect = d.__getitem__
  return m

Answered By - Manu