def test_passes_with_unused_negative_weights():
graph = Graph()
nodes = [["a","b", 4], ["c", "d", -1]]
graph.make_weighted_from_list(nodes)
actual_path = graph.dijkstras_with_target(start=Node("a"), target=Node("b"))
expected_path = ["a", "b"]
assert actual_path == expected_path
def test_with_disconnected_nodes():
graph = Graph()
nodes = [["a"], ["b"]]
graph.make_unweighted_from_list(nodes)
actual_path = graph.dijkstras_with_target(start=Node("a"), target=Node("b"))
expected_path = []
assert actual_path == expected_path
def test_cyclic_graph():
graph = Graph()
nodes = [["a","b"], ["b","c"], ["b", "a"], ["b", "z"], ["c", "d"], ["c", "e"], ["e", "a"]]
graph.make_unweighted_from_list(nodes)
expected_path = ["a", "b", "c", "e"]
actual_path = graph.dijkstras_with_target(start=Node("a"), target=Node("e"))
assert actual_path == expected_path
def test_straight_line_graph():
# a straight line graph is one that has only one path at each node
graph = Graph()
nodes = [["a","b",1],["b","c",1]]
graph.make_weighted_from_list(nodes)
expected_path = ["a","b","c"]
actual_path = graph.dijkstras_with_target(Node("a"),Node("c"))
assert actual_path == expected_path
def test_strongly_connected_graph():
graph = Graph()
nodes = []
nodes_to_add = set(["a","b","c","d","e","f","g","h","i"])
for node in nodes_to_add:
for other_node in nodes_to_add:
if other_node != node:
nodes.append([node,other_node])
graph = Graph()
graph.make_unweighted_from_list(nodes, directed=False)
actual_path = graph.dijkstras_with_target(start = Node("f"), target = Node("i"))
expected_path = ["f","i"]
assert actual_path == expected_path
def test_fails_with_negative_weights():
graph = Graph()
nodes = [["a","b", -1], ["c", "d", 4]]
graph.make_weighted_from_list(nodes)
with raises(DijkstrasException):
graph.dijkstras_with_target(start=Node("a"), target=Node("b"))
