def test_internal_node_removal():
network = Network()
network.add_node("A")
network.add_node("B")
network.add_node("C")
network.add_node("D")
network.add_edge("A", "B")
network.add_edge("B", "C")
network.add_edge("C", "D")
network.add_edge("A", "C") # Useful for ensuring the ending list
# is deterministic.
# Ensure that we can't remove an internal node without a ValueError
# by default.
with pytest.raises(ValueError):
network.prune_node("B")
# OK. Now that we know that works, let's prune it harder.
network.prune_node("B", remove_backrefs=True)
# And make sure "B" is gone.
assert list(network.sort()) == ["A", "C", "D"]
