void InternalTest(int?[] tree, bool expected)
{
TreeNode root = TreeNode.Get(tree);
bool actual = ValidateBST.IsValidBST(root);
Assert.Equal <bool>(expected, actual);
}
public void ValidateBSTTest(TreeNode <int> root, bool expected)
{
bool result = ValidateBST.IsValidBST(root, int.MinValue, int.MaxValue);
Assert.Equal(expected, result);
}
