def METHOD_NAME(self):
    self.assertEqual(pybamm.rmse(np.ones(5), np.zeros(5)), 1)
    self.assertEqual(pybamm.rmse(2 * np.ones(5), np.zeros(5)), 2)
    self.assertEqual(pybamm.rmse(2 * np.ones(5), np.ones(5)), 1)
    x = np.array([1, 2, 3, 4, 5])
    self.assertEqual(pybamm.rmse(x, x), 0)
    with self.assertRaisesRegex(ValueError, "same length"):
        pybamm.rmse(np.ones(5), np.zeros(3))