def test_remove_missing_node_raises_undirected():
# given
g = UndirectedGraph()
g.add_node(1)
g.add_node(2)
g.add_node(3)
# when
with pytest.raises(DoesNotExistError):
g.remove_node(4)
def test_remove_node_removes_edges_too_undirected():
# given
g = UndirectedGraph()
# when
g.add_edge(1, 3)
g.add_edge(3, 1)
g.add_edge(5, 1)
g.add_edge(1, 6)
g.remove_node(1)
assert (1, 3) not in g.edges
assert (3, 1) not in g.edges
assert (5, 1) not in g.edges
assert len(g.edges) == 0