def METHOD_NAME(self) -> None:
    """Makes sure that once two nodes are joined, they do not split"""
    union_find = UnionFind()
    union_find.add(1)
    union_find.union(1, 2)
    self.assertEqual(union_find.find(1), 2)
    self.assertEqual(union_find.find(2), 2)
    union_find.add(1)
    union_find.add(2)
    self.assertEqual(union_find.find(1), 2)
    self.assertEqual(union_find.find(2), 2)