Number, operator overloading, unittest

import unittest

class Number:
    def __init__(self, value):
        self.value = value


    def __add__(self, other_Number):
        """
        teaching how to sum two instances of Number
        """
        return Number(self.value+other_Number.value)

class NumberTest(unittest.TestCase):

    def setUp(self):
        self.one = Number(1)
        self.two = Number(2)

    def test_add(self):
        # first assertion
        self.assertEqual(
            (self.one + self.two).value,
            self.one.value + self.two.value
        )

        # second assertion
        self.assertEqual(
            (self.one + self.two).value,
            Number(3).value
        )

# it'll run the test if the script is started by terminal, not imported
if __name__ == '__main__':
    unittest.main()