def test_prefs(self):
p = Preferences([1, 2, 3, 4, 5])
self.assertTrue(p.prefers(1, 2))
self.assertFalse(p.prefers(2, 1))
self.assertTrue(p.prefers(2, 5))
self.assertTrue(p.prefers(2, 3))
self.assertTrue(p.prefers(1, 5))
self.assertFalse(p.prefers(5, 1))
self.assertFalse(p.prefers(5, 5))
self.assertFalse(p.prefers(5, 10))
self.assertEqual([1, 2, 3, 4, 5], list(p))
def test_string_keys(self):
p = Preferences(('A', 'B'))
self.assertTrue(p.prefers('A', 'B'))
self.assertFalse(p.prefers('B', 'A'))
self.assertEqual({'A'}, set(p.all_preferred_to('B')))
