def test_connectivity_on_removal(edges):
# check that when nodes are removed in reverse topological order
# connectivity of the DAG is maintained, i.e. remaining nodes
# are reachable from the root.
root = 1
tr = Trace()
for e1, e2 in edges:
tr.add_edge(e1, e2)
top_sort = tr.topological_sort()
while top_sort:
num_nodes = len([n for n in tr._dfs(root, set())])
num_expected = len(top_sort)
assert_equal(num_nodes, num_expected)
tr.remove_node(top_sort.pop())
def test_topological_sort(edges):
tr = Trace()
for n1, n2 in edges:
tr.add_edge(n1, n2)
top_sort = tr.topological_sort()
# check all nodes are accounted for exactly once
expected_nodes = set().union(*edges)
assert len(top_sort) == len(expected_nodes)
assert set(top_sort) == expected_nodes
# check no edge ordering is violated
ranks = {n: rank for rank, n in enumerate(top_sort)}
for n1, n2 in edges:
assert ranks[n1] < ranks[n2]
