def METHOD_NAME(self):
    def test_method():
        pass
    octoprint.plugin.BlueprintPlugin.errorhandler(404)(test_method)
    self.assertTrue(hasattr(test_method, "_blueprint_error_handler"))
    self.assertTrue("test_method" in test_method._blueprint_error_handler)
    self.assertTrue(len(test_method._blueprint_error_handler["test_method"]) == 1)
    self.assertListEqual(test_method._blueprint_error_handler["test_method"], [404])