def test_remove_missing_edge_raises_undirected():
# given
g = UndirectedGraph()
g.add_edge(1, 2)
g.add_edge(2, 3)
g.add_edge(3, 1)
# when
with pytest.raises(DoesNotExistError):
g.remove_edge(2, 4)
def test_remove_edge_undirected():
# given
g = UndirectedGraph()
g.add_edge(1, 2)
g.add_edge(2, 3)
g.add_edge(3, 1)
# when
g.remove_edge(2, 1)
# then
assert (1, 2) not in g.edges
assert (2, 1) not in g.edges
assert len(g.edges) == 2
assert len(g.nodes) == 3