def test_del_node():
_graph = Graph()
_node1 = Node(4)
_node2 = Node(5)
_graph.add_edges(_node1, _node2, 1)
_graph.del_node(_node2)
assert _graph.graph == {'n0': {}}
_node3 = Node(6)
_node4 = Node(7)
_graph.add_edges(_node1, _node2, 1)
_graph.add_edges(_node3, _node4, 1)
_graph.add_edges(_node2, _node4, 1)
_graph.del_node(_node4)
assert _graph.graph == {'n0': {'n1': 1}, 'n1': {'n0': 1}, 'n3': {}}
