def test_nodes_reachable_from(self):
"""
Tests finding all nodes reachable from a single node.
"""
# Simple situation first.
g = DAG()
g.add_node(1)
g.add_node(2)
g.add_node(3)
g.add_edge(1, 2)
g.add_edge(2, 3)
self.assertEqual(len(g.nodes_reachable_from(1)), 2)
self.assertIn(2, g.nodes_reachable_from(1))
self.assertIn(3, g.nodes_reachable_from(1))
self.assertEqual(len(g.nodes_reachable_from(2)), 1)
self.assertIn(3, g.nodes_reachable_from(1))
# No nodes reachable from the given node
g = DAG()
g.add_node(1)
g.add_node(2)
g.add_node(3)
g.add_edge(2, 3)
self.assertEqual(len(g.nodes_reachable_from(1)), 0)
# More complex graph
g = DAG()
g.add_node(1)
g.add_node(2)
g.add_node(3)
g.add_node(4)
g.add_node(5)
g.add_edge(1, 3)
g.add_edge(2, 4)
g.add_edge(2, 5)
g.add_edge(4, 5)
g.add_edge(5, 3)
self.assertEqual(len(g.nodes_reachable_from(2)), 3)
for node in range(3, 6):
self.assertIn(node, g.nodes_reachable_from(2))
self.assertEqual(len(g.nodes_reachable_from(1)), 1)
self.assertIn(3, g.nodes_reachable_from(1))
