How to mock a Django model object (along with its methods)?

Question

I'm trying to mock a chained Django model object in the following dummy method,

# utils.py
def foo_something_exist():
   if Foo.objects.get(a='something').exist():
      return 'exist'



# test.py
import unittest.mock import patch

import utils

.
.
.
@patch('utils.Foo')
def test_foo_something_exist_returns_none(self, mock_foo):
   mock_foo.objects.get.exists.return_value = False
   self.assertIsNone(utils.foo_something_exist()) 
.
.
.

test_foo_something_exist() fails the test. I discovered that Foo.objects.get(a='something').exist() in utils.py was a MagicMock object (<MagicMock name='Member.objects.get().exists()' id='xxxxxx'>) instead of False, which contributed to the failure of this test function. And yes, I've also tried mock_foo.objects.return_value.get.return_value.exists.return_value = False, which was mentioned in a post. Pointers/hints for correctly mocking a model object (with its chained methods) is appreciate.

Thank you in advance.

Answer 1

Don't patch the model itself but model.objects and then mock every part of the chain:

@patch('utils.Foo.objects')
def test_foo_something_exist_returns_none(self, mock_foo):
    # just to show how to do it with longer chains
    # mock_foo.filter.return_value = mock_foo
    # mock_foo.exclude.return_value = mock_foo            
    mock_foo.get.return_value = mock_foo
    mock_foo.exists.return_value = False

    self.assertIsNone(utils.foo_something_exist()) 

This also work's with .filter(), .exclude() and other model operations. I also find Model Mommy really helpful when testing Django models.