def test_christofides_hamiltonian():
random.seed(42)
G = nx.complete_graph(20)
for (u, v) in G.edges():
G[u][v]["weight"] = random.randint(0, 10)
H = nx.Graph()
H.add_edges_from(pairwise(nx_app.christofides(G)))
H.remove_edges_from(nx.find_cycle(H))
assert len(H.edges) == 0
tree = nx.minimum_spanning_tree(G, weight="weight")
H = nx.Graph()
H.add_edges_from(pairwise(nx_app.christofides(G, tree)))
H.remove_edges_from(nx.find_cycle(H))
assert len(H.edges) == 0
def test_christofides_ignore_selfloops():
G = nx.complete_graph(5)
G.add_edge(3, 3)
cycle = nx_app.christofides(G)
assert len(cycle) - 1 == len(G) == len(set(cycle))