def test_graph_depth_first():
graph = Graph()
v1 = graph.add_node('a')
v2 = graph.add_node('b')
v3 = graph.add_node('c')
v4 = graph.add_node('d')
v5 = graph.add_node('e')
v6 = graph.add_node('f')
v7 = graph.add_node('g')
v8 = graph.add_node('h')
graph.add_edge(v1, v2)
graph.add_edge(v1, v4)
graph.add_edge(v2, v1)
graph.add_edge(v2, v3)
graph.add_edge(v2, v4)
graph.add_edge(v3, v2)
graph.add_edge(v3, v7)
graph.add_edge(v4, v1)
graph.add_edge(v4, v2)
graph.add_edge(v4, v5)
graph.add_edge(v4, v8)
graph.add_edge(v4, v6)
graph.add_edge(v6, v4)
graph.add_edge(v6, v8)
graph.add_edge(v8, v6)
graph.add_edge(v8, v4)
graph.add_edge(v5, v4)
values = graph.depth_first(v1)
actual = [vertex.value for vertex in values]
assert actual == ['a', 'b', 'a', 'd', 'e', 'h', 'f', 'c', 'g']
def test_neighbors_three():
g = Graph()
vertex_a = g.add('a')
vertex_b = g.add('b')
vertex_c = g.add('c')
vertex_d = g.add('d')
vertex_e = g.add('e')
vertex_f = g.add('f')
vertex_g = g.add('g')
vertex_h = g.add('h')
g.add_edge(vertex_a, vertex_b)
g.add_edge(vertex_c, vertex_g)
g.add_edge(vertex_b, vertex_c)
g.add_edge(vertex_b, vertex_d)
g.add_edge(vertex_e, vertex_d)
g.add_edge(vertex_d, vertex_h)
g.add_edge(vertex_f, vertex_h)
g.add_edge(vertex_d, vertex_f)
g.add_edge(vertex_d, vertex_a)
actual = g.depth_first('f')
assert actual == ['f', 'h', 'd', 'b', 'a', 'c', 'g', 'e']