def test_add_vertex(self):
g = Graph()
g.add_vertex('A')
g.add_vertex('B')
g.add_vertex('C')
g.add_vertex('D')
assert g.has_vertex('A') is True
assert g.has_vertex('B') is True
assert g.has_vertex('C') is True
assert g.has_vertex('D') is True
assert g.has_vertex('E') is False
assert g.has_vertex('F') is False
assert g.has_vertex('G') is False
assert g.has_vertex('H') is False
g.add_edge('A', 'B')
g.add_edge('C', 'D')
self.assertCountEqual(g.get_neighbors('A'), ['B'])
self.assertCountEqual(g.get_neighbors('B'), [])
self.assertCountEqual(g.get_neighbors('C'), ['D'])
self.assertCountEqual(g.get_neighbors('D'), [])
g.add_edge('A', 'F')
g.add_edge('B', 'E')
self.assertCountEqual(g.get_neighbors('A'), ['B', 'F'])
self.assertCountEqual(g.get_neighbors('B'), ['E'])
def test_get_neighbors(self):
g = Graph()
g.add_edge('A', 'B')
g.add_edge('C', 'D')
g.add_edge('E', 'F')
g.add_edge('G', 'H')
self.assertCountEqual(g.get_neighbors('A'), ['B'])
self.assertCountEqual(g.get_neighbors('B'), [])
self.assertCountEqual(g.get_neighbors('C'), ['D'])
self.assertCountEqual(g.get_neighbors('D'), [])
with self.assertRaises(KeyError):
g.get_neighbors('Z')
