Python Value Object using namedtuple

PythonValueObject.py

# Tested with Python 3.5

from unittest import TestCase, main
from collections import namedtuple
import math


class Point(namedtuple('Point', 'x, y')):

    def get_distance_from_origin(self):
        return math.sqrt(self.x**2 + self.y**2)

    def set_x(self, new_x):
        self.x = new_x


class TestValueObject(TestCase):

    def test_can_construct(self):
        point = Point(y=2, x=4)
        self.assertEqual(point.x, 4)
        self.assertEqual(point.y, 2)

    def test_cannot_modify_fields(self):
        point = Point(y=2, x=4)

        with self.assertRaises(AttributeError):
            point.x = 32202

        with self.assertRaises(AttributeError):
            point.y = 32202

    def test_cannot_construct_without_constructor_arguments(self):
        with self.assertRaises(TypeError):
            Point()

    def test_can_call_method(self):
        point = Point(x=3, y=4)
        self.assertEqual(point.get_distance_from_origin(), 5)

    def test_cannot_modify_fields_from_the_inside(self):
        point = Point(x=4, y=2)

        with self.assertRaises(AttributeError):
            point.set_x(32202)


if __name__ == '__main__':
    main()