def test_is_connected_sees_non_connected_graph(self):
a, b, c, d = Vertex('a'), Vertex('b'), Vertex('c'), Vertex('d')
e = Vertex('e')
g = Graph([a, b, c, d, e])
g.add_edge(Edge(a, b))
g.add_edge(Edge(b, c))
g.add_edge(Edge(c, d))
g.add_edge(Edge(d, a))
self.assertFalse(g.is_connected())
def test_is_connected_sees_connected_graph(self):
"""a graph is connected if there is a path
from every node to every other node"""
a, b, c, d = Vertex('a'), Vertex('b'), Vertex('c'), Vertex('d')
g = Graph([a, b, c, d])
g.add_edge(Edge(a, b))
g.add_edge(Edge(b, c))
g.add_edge(Edge(c, d))
g.add_edge(Edge(d, a))
self.assertTrue(g.is_connected())
