unittest MagicMock

what is it?

a subclass of unittest Mock with default implementations of most of the magic methods. You can use MagicMock without having to configure the magic methods yourself

methods are preconfigured with a default return value:

• __lt__: NotImplemented
• __gt__: NotImplemented
• __le__: NotImplemented
• __ge__: NotImplemented
• __int__: 1
• __contains__: False
• __len__: 0
• __iter__: iter([])
• __exit__: False
• __aexit__: False
• __complex__: 1j
• __float__: 1.0
• __bool__: True
• __index__: 1
• __hash__: default hash for the mock
• __str__: default str for the mock
• __sizeof__: default sizeof for the mock

patching defaults

set the return_value:

>>> MagicMock() == 3
False
>>> MagicMock() != 3
True
>>> mock = MagicMock()
>>> mock.__eq__.return_value = True
>>> mock == 3
True

more complex example

mocking a call to a db (link to medium article)

@patch("snowflake.connector.connect")
@mock.create_autospec
def test_snowflake_query(mocker):
    mock_conn = MagicMock()
    mocker.patch("snowflake.connector.connect", return_value=mock_conn)
 
    mock_cur = MagicMock()
    mock_conn.cursor.return_value = mock_cur
 
    mock_fetchall = MagicMock(return_value=expected_return_value)
    mock_cur.fetchall = mock_fetchall
 
	mock_fetchall.assert_called_once()
	assert result == expected_return_value