'When the default manager of the model is a custom manager,
it needs to be added to the model state.'

def test_custom_default_manager_added_to_the_model_state(self):

    new_apps = Apps(['migrations'])
    custom_manager = models.Manager()
    class Author(models.Model, ):
        objects = models.TextField()
        authors = custom_manager
        class Meta:
            app_label = 'migrations'
            apps = new_apps
    project_state = ProjectState.from_apps(new_apps)
    author_state = project_state.models[('migrations', 'author')]
    self.assertEqual(author_state.managers, [('authors', custom_manager)])
