final double tolerance = 1.0e-12;
// at original points
for (int i=0; i<N; i++) {
final double p = x.get(i);
final double calculated = f.op(p);
final double expected = y.get(i);
assertFalse("failed to reproduce expected datum"
+"\n expected value: "+expected
+"\n calculated value: "+calculated
+"\n error: "+Math.abs(calculated-expected),