### Question:
ButterworthIIRDesigner extends AbstractIIRDesigner { @Override protected FilterZerosPolesGain calculatePrototype(int filterOrder, double gpass, double gstop) { return calculatePrototype(filterOrder); }    }### Answer:
@Test public void testCalculatePrototype() { FilterZerosPolesGain zpk1 = iirdesigner.calculatePrototype(3); Complex[] poles = new Complex[] {new Complex(-0.5, 8.66025404e-1), new Complex(-1.0, 0.0), new Complex(-0.5, -8.66025404e-1)}; FilterZerosPolesGain zpk2 = new FilterZerosPolesGain(new Complex[0], poles, 1.0); assertEquals(zpk1, zpk2); }