def METHOD_NAME(self):
    set_attr_on_json_field(
        self.instance, 'config.value_display.tree.diameter.units', 'ft')
    self.tree.convert_to_display_units()
    self.tree.diameter = 1
    self.tree.convert_to_database_units()
    self.tree.save_with_user(self.user)
    updated_tree = Tree.objects.get(pk=self.tree.pk)
    self.assertAlmostEqual(12, updated_tree.diameter)