def test_delete_first(self):
expected = PositionalList.from_iterable('bc')
pl = PositionalList()
a = pl.add_first('a')
b = pl.add_after(a, 'b')
c = pl.add_last('c')
db = pl.delete(a)
self.assertEqual(pl, expected)
self.assertEqual(db, 'a')
def test_delete_len(self):
pl = PositionalList()
a = pl.add_first('a')
b = pl.add_after(a, 'b')
c = pl.add_last('c')
d = pl.add_after(c, 'd')
self.assertEqual(len(pl), 4)
pl.delete(a)
self.assertEqual(len(pl), 3)
pl.delete(pl.first())
self.assertEqual(len(pl), 2)
pl.delete(pl.last())
self.assertEqual(len(pl), 1)
self.assertTrue(pl)
pl.delete(c)
self.assertEqual(len(pl), 0)
self.assertFalse(pl)