How do you mock a readonly property with mock?
I tried:
setattr(obj.__class__, 'property_to_be_mocked', mock.Mock())
but the issue is that it then applies to all instances of the class... which breaks my tests.
Do you have any other idea? I don't want to mock the full object, only this specific property.
I think the better way is to mock the property as PropertyMock
, rather than to mock the __get__
method directly.
It is stated in the documentation, search for unittest.mock.PropertyMock
:
A mock intended to be used as a property, or other descriptor, on a class. PropertyMock
provides __get__
and __set__
methods so you can specify a return value when it is fetched.
Here is how:
class MyClass:
@property
def last_transaction(self):
# an expensive and complicated DB query here
pass
def test(unittest.TestCase):
with mock.patch('MyClass.last_transaction', new_callable=PropertyMock) as mock_last_transaction:
mock_last_transaction.return_value = Transaction()
myclass = MyClass()
print myclass.last_transaction
mock_last_transaction.assert_called_once_with()