def test_topological_sort_cyclic_graph():
graph = DiGraph()
for node in [0, 1, 2]:
graph.add_node(node)
graph.add_edge(0, 1)
graph.add_edge(1, 2)
graph.add_edge(2, 0)
with pytest.raises(CyclicDiGraphError):
graph.topological_sort()
def test_topological_sort():
# Example randomly generated with
# https://www.cs.usfca.edu/~galles/visualization/TopoSortDFS.html
graph = DiGraph()
for node in range(8):
graph.add_node(node)
graph.add_edge(0, 2)
graph.add_edge(0, 3)
graph.add_edge(2, 4)
graph.add_edge(2, 6)
graph.add_edge(4, 7)
graph.add_edge(6, 7)
graph.add_edge(3, 5)
graph.add_edge(1, 5)
graph.add_edge(3, 7)
assert [1, 0, 3, 5, 2, 6, 4, 7] == graph.topological_sort()
def test_topological_sort_single_node():
graph = DiGraph()
graph.add_node(0)
assert [0] == graph.topological_sort()
def test_topological_sort_empty_graph():
graph = DiGraph()
assert [] == graph.topological_sort()
