public void TestHessian(double[] arr, params double[][] expected)
{
Derivative = new Derivative(TypicalMultivariateFunction);
var vector = new Vector(arr);
var hessian = Derivative.GetHessian(vector);
var got = hessian.Items;
for (int i = 0; i < 2; i++)
{
Assert.AreEqual(expected[i], got[i]);
}
}