def test_large_vs_known_implementation():
"""
Creates a large random graph and runs dijkstra's algorithm with this implementation
as well as a known good implementation I grabbed from github. Compares that the results
returned are the same
"""
import random
size = 1000
my_graph = Graph()
my_nodes = []
other_graph = OtherGraph()
for i in range(size):
start_node = i
end_node = random.randint(0, size)
length = random.randrange(0, 10000)
my_nodes.append([start_node, end_node, length])
other_graph.add_edge(start_node, end_node, length)
my_graph.make_weighted_from_list(my_nodes)
my_prev, my_unvisited = my_graph.dijkstra(start=Node(0))
other_visited, other_prev = known_dijkstras_implementation(other_graph, 0)
unvisited_diff = my_unvisited.keys() - other_visited.keys()
visited_diff = other_visited.keys() - my_unvisited.keys()
assert my_prev == other_prev and my_unvisited.keys() == unvisited_diff and other_visited.keys() == visited_diff
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_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_weighted_undirected():
graph = Graph()
nodes = [["a","b",1],["b","c",2],["a","c",3]]
graph.make_weighted_from_list(nodes, directed=False)
test_graph = {
Node("a"):[Edge("a", "b",1), Edge("a","c",3)],
Node("b"):[Edge("b","a",1), Edge("b","c",2)],
Node("c"):[Edge("c","b",2), Edge("c","a",3)]
}
assert compare_graphs(test_graph, graph.graph) == True
def test_weighted_modify_weight():
graph = Graph()
nodes = [["a","b",1],["b","c",2],["a","c",3]]
graph.make_weighted_from_list(nodes)
graph.modify_weight(["a","b",1], 78)
test_graph = {
Node("a"):[Edge("a", "b",78), Edge("a","c",3)],
Node("b"):[Edge("b","c",2)],
Node("c"):[]
}
assert compare_graphs(test_graph, graph.graph) == True
def test_weighted_add_node():
graph = Graph()
nodes = [["a","b",5],["b","c",4],["a","c",3]]
graph.make_weighted_from_list(nodes)
graph.add_node(["b","b",2])
graph.add_node(["b","d",1])
test_graph = {
Node("a"):[Edge("a","b",5),Edge("a","c",3)],
Node("b"):[Edge("b","c",4),Edge("b","b",2),Edge("b","d",1)],
Node("c"):[],
Node("d"):[]
}
assert compare_graphs(test_graph, graph.graph) == True
def test_weighted_remove_node():
graph = Graph()
nodes = [["a","b",1],["b","b",99],["c","b",2],["d","b",3],["e","b",4],["f","z","a"]]
graph.make_weighted_from_list(nodes)
graph.remove_node(Node("b"))
test_graph = {
Node("a"):[],
Node("c"):[],
Node("d"):[],
Node("e"):[],
Node("f"):[Edge("f","z","a")],
Node("z"): []
}
assert compare_graphs(test_graph, graph.graph) == True
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"))
