/**
*
*/
@Test(expectedExceptions = IllegalArgumentException.class)
public void nullPpDiffTwiceX0MultiTest() {
PiecewisePolynomialResult2D result = new PiecewisePolynomialResult2D(knots0, knots1, coefs, new int[] {5, 4 });
PiecewisePolynomialFunction2D function = new PiecewisePolynomialFunction2D();
final int n0Keys = 21;
final int n1Keys = 31;
double[] x0Keys = new double[n0Keys];