1 /* Sample of Recursion and JUnit
   2  */
   3 
   4 import junit.framework.*;
   5 
   6 class FactorialException extends ArithmeticException {
   7 }
   8 
   9 class Factorial {
  10     private int fact(int aNum) {
  11         if(aNum < 1)
  12             throw new FactorialException();
  13         if(aNum == 1)
  14             return 1;
  15         else 
  16             return aNum * fact(aNum-1);
  17     }
  18     public int get(int aNum) {
  19         return fact(aNum);
  20     }
  21 }
  22 
  23 public class FactorialTest extends TestCase {
  24     public static void main(String[] args) {
  25         junit.textui.TestRunner.run(FactorialTest.class);
  26     }
  27     Factorial f = new Factorial();
  28     public void test1() {
  29         assertEquals(1, f.get(1));
  30     }
  31     public void test2() {
  32         assertEquals(2, f.get(2));
  33     }
  34     public void testNegative() {
  35         int impossible;
  36         try {
  37             impossible = f.get(-2);
  38             fail("Factorial input must positive");
  39         } catch (FactorialException success) {
  40         }
  41     }
  42 }