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_add_node_already_graph_does_nothing():
# given
g = UndirectedGraph()
# when
g.add_edge(1, 3)
g.add_edge(3, 1)
g.add_edge(5, 1)
g.add_node(3)
assert len(g.neighbors(3)) == 1
assert len(g.nodes) == 3
def test_undirected_add_node_and_list():
# given
g = UndirectedGraph()
# when
g.add_node(1)
g.add_node("a")
g.add_node(42)
# then
assert set(g.nodes) == {1, 42, "a"}