def test_encode(self):
     tiny_url = TinyURL()
     self.assertEqual(
         tiny_url._encode(0), '0')
     self.assertEqual(
         tiny_url._encode(10), 'a')
     self.assertEqual(
         tiny_url._encode(62), '10')
 def test_generate(self):
     tiny_url = TinyURL()
     self.assertEqual(
         tiny_url.generate('aaa'), '0')
 def test_lookup(self):
     tiny_url = TinyURL()
     self.assertEqual(
         tiny_url.lookup(tiny_url.generate('bbb')), 'bbb')
     self.assertEqual(
         tiny_url.lookup('ccc'), None)