3 ways to mock a Django model that is passed into a function as a parameter

mocking_a_django_model.py

import json
from django.db.models import Model
from typing import Type
from unittest.mock import MagicMock
from types import SimpleNamespace
from collections import namedtuple


def get_list_of_field_names(DjangoModel: Type[Model]) -> list:
    return list(map(lambda x: x.name, DjangoModel._meta.fields))


def test_using_magicmock():
    MockedDjangoModel = MagicMock(name="MockedDjangoModel")
    field0 = MagicMock()
    field0.name = "field0"
    field1 = MagicMock()
    field1.name = "field1"
    MockedDjangoModel._meta.fields = (field0, field1)
    assert get_list_of_field_names(MockedDjangoModel) == ["field0", "field1"]


def test_using_simplenamespace():
    """This is a trick to get a similar result using SimpleNamespace.  Since it uses
    json.dumps, it only works for JSON serializable dictionary values.  If the dictionary
    contains a Python object, this will throw:
    TypeError: Object of type type is not JSON serializable
    Ref: https://docs.python.org/3/library/json.html#json.load
    """
    # Ref: https://stackoverflow.com/questions/50490856/creating-a-namespace-with-a-dict-of-dicts
    d = {"_meta": {"fields": ({"name": "field0"}, {"name": "field1"})}}
    MockedDjangoModel = json.loads(
        json.dumps(d), object_hook=lambda d: SimpleNamespace(**d)
    )
    assert get_list_of_field_names(MockedDjangoModel) == ["field0", "field1"]


def test_using_namedtuple():
    """In theory this could work too, but named tuple field names cannot start with an
    underscore for whatever reason
    Ref: https://docs.python.org/3/library/collections.html#collections.namedtuple
    """
    d = {"_meta": {"fields": ({"name": "field0"}, {"name": "field1"})}}
    try:
        MockedDjangoModel = json.loads(
            json.dumps(d),
            object_hook=lambda d: namedtuple(
                "MockedDjangoModel", d.keys(), defaults=d.values(),
            )(),
        )
        assert get_list_of_field_names(MockedDjangoModel) == ["field0", "field1"]
    except ValueError as e:
        print(repr(e))  # Field names cannot start with an underscore: '_meta'