def test_add_by_value_to_empty(self):
"""Test adding a single item to empty bimap by value."""
bimap = BiMap()
bimap.add_value("first", 1)
self.assertEqual({1: "first"}, bimap.get_key_to_value())
self.assertEqual(1, len(bimap))
self.assertEqual(1, bimap.get_value("first"))
self.assertEqual("first", bimap.get_key(1))
def test_add_to_nonempty(self):
"""Test adding a single item to nonempty bimap."""
bimap = BiMap({1: "first", 2: "second"})
bimap.add_key(3, "third")
bimap.add_value("fourth", 4)
self.assertEqual(4, len(bimap))
self.assertEqual("second", bimap.get_key(2))
self.assertEqual("fourth", bimap.get_key(4))
self.assertEqual(3, bimap.get_value("third"))