public void testGetUnseenFreq() {
   assertEquals(0.0, fd.getFreq("a"));
   fd.inc("b", 2);
   assertEquals(0.0, fd.getFreq("a"));
   fd.inc("b");
   assertEquals(0.0, fd.getFreq("a"));
 }
 public void testFreq() {
   fd.inc("a", 1);
   assertEquals(1.0, fd.getFreq("a"));
   fd.inc("b", 1);
   assertEquals(0.5, fd.getFreq("a"));
   assertEquals(0.5, fd.getFreq("b"));
   fd.inc("a", 1);
   assertEquals(2.0 / 3L, fd.getFreq("a"), 0.001);
   assertEquals(1.0 / 3L, fd.getFreq("b"), 0.001);
 }