def test_undirected_graph_vertices_and_edges(self):
""" Get undirected graphs' vertices and edges properties """
g = UndirectedGraph()
g.add_vertex(v_val='v0')
g.add_vertex(v_val='v1')
g.add_edge(('v0', 'v1'))
v0 = g.get_vertex('v0')
v1 = g.get_vertex('v1')
e01 = g.get_edge(('v0', 'v1'))
self.assertEqual(set(g.vertices), set([v0, v1]))
self.assertEqual(set(g.edges), set([e01]))
with self.assertRaises(AttributeError):
g.vertices = set()
with self.assertRaises(AttributeError):
g.edges = set()
