def test_arbitrary_node():
# given
g = UndirectedGraph()
g.add_edge(1, 2)
g.add_edge(2, 3)
u = g.arbitrary_node()
assert u in g.nodes
def test_undirected_graphs_have_no_self_loops():
# given
g = UndirectedGraph()
# when
with pytest.raises(ValueError):
g.add_edge(1, 1)
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_undirected_graph_add_edge_adds_node():
# given
g = UndirectedGraph()
# when
g.add_edge(1, 3)
# then
assert 1 in g.adj
assert 3 in g.adj
def test_undirected_add_edge_twice_only_adds_one_edge():
# given
g = UndirectedGraph()
# when
g.add_edge(1, 3)
g.add_edge(3, 1)
# then
[edge] = g.edges
assert set(edge) == {1, 3}
def test_undirected_number_of_edges():
# given
g = UndirectedGraph()
# when
g.add_edge(1, 3)
g.add_edge(3, 1)
g.add_edge(5, 1)
g.add_edge(1, 6)
assert len(g.edges) == 3
def test_undirected_neighbors():
# given
g = UndirectedGraph()
# when
g.add_edge(1, 3)
g.add_edge(3, 1)
g.add_edge(5, 1)
g.add_edge(1, 6)
# then
assert set(g.neighbors(1)) == {3, 5, 6}
assert set(g.neighbors(6)) == {1}
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_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
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
def test_undirected_has_edge():
# given
g = UndirectedGraph()
# when
g.add_edge(1, 3)
g.add_edge(3, 1)
g.add_edge(5, 1)
g.add_edge(1, 6)
# then
assert (1, 3) in g.edges
assert (3, 1) in g.edges
assert (5, 1) in g.edges
assert (1, 5) in g.edges
assert (1, 999) not in g.edges