def test_empty_url_not_valid(self):
        url = ''

        self.assertFalse(url_shortener.url_valid(url))
    def test_url_with_htp_not_valid(self):
        url = 'htp://www.google.com'

        self.assertFalse(url_shortener.url_valid(url))
    def test_url_without_protocol_not_valid(self):
        url = 'www.google.com'

        self.assertFalse(url_shortener.url_valid(url))
    def test_url_with_https_valid(self):
        url = 'https://www.google.com'

        self.assertTrue(url_shortener.url_valid(url))