def test_remove_edge_notthere(self):
g = Graph([v, w, x], [vw, vx])
g.del_edge(wx)
assert g == Graph([v, w, x], [vw, vx])
def test_del_edge(self):
g = Graph([v, w, x], [vw, vx])
g.del_edge(vx)
assert g == Graph([v, w, x], [vw])
g.del_edge(wv) # backwards vw
assert g == Graph([v, w, x], [])
