Also test failure case of ProjectState dependency resolution

from django.test import TestCase

from django.db import models

from django.db.models.loading import BaseAppCache

from django.db.migrations.state import ProjectState, ModelState

from django.db.migrations.state import ProjectState, ModelState, InvalidBasesError

class StateTests(TestCase):

        project_state.add_model_state(ModelState.from_model(F))

        final_app_cache = project_state.render()

        self.assertEqual(len(final_app_cache.get_models()), 6)

        # Now make an invalid ProjectState and make sure it fails

        project_state = ProjectState()

        project_state.add_model_state(ModelState.from_model(A))

        project_state.add_model_state(ModelState.from_model(B))

        project_state.add_model_state(ModelState.from_model(C))

        project_state.add_model_state(ModelState.from_model(F))

        with self.assertRaises(InvalidBasesError):

            project_state.render()