@Test
 public void testNotEquals() throws Exception {
   String Id1 = "1";
   String Id2 = "2";
   Clock clock1 = new Clock(Id1);
   clock1.addNode(Id2, 2);
   Clock clock2 = new Clock(Id2);
   clock2.addNode(Id1, 1);
   Assert.assertTrue(!clock1.equals(clock2));
 }
 @Test
 public void testEquivalent() throws Exception {
   String Id1 = "1";
   String Id2 = "2";
   Clock cl1 = new Clock(Id1);
   Clock cl2 = new Clock(Id2);
   cl1.addNode(Id1, 1);
   cl1.addNode(Id2, 2); // cl1 = {1,2}
   cl2.addNode(Id1, 2);
   cl2.addNode(Id2, 1); // cl2 = {2,1}
   Assert.assertTrue(cl2.equivalent(cl1));
 }
 @Test
 public void testIsLower() {
   String Id1 = "1";
   String Id2 = "2";
   Clock cl1 = new Clock(Id1);
   Clock cl2 = new Clock(Id2);
   cl1.addNode(Id1, 0);
   cl1.addNode(Id2, 0);
   cl2.addNode(Id1, 2);
   cl2.addNode(Id2, 2);
   cl2.incrementClock();
   Assert.assertTrue(cl1.isLower(cl2));
 }
 @Test
 public void testIsGreaterOrEqual() throws Exception {
   String Id1 = "1";
   String Id2 = "2";
   Clock cl1 = new Clock(Id1);
   Clock cl2 = new Clock(Id2);
   cl1.addNode(Id1, 0);
   cl1.addNode(Id2, 1);
   cl2.addNode(Id1, 0);
   cl2.addNode(Id2, 1);
   cl1.incrementClock();
   Assert.assertTrue(cl1.isGreaterOrEqual(cl2));
 }
  @Test
  public void testSetVector() throws Exception {
    String Id1 = "1";
    String Id2 = "2";
    Clock c1 = new Clock(Id1);
    Clock c2 = new Clock(Id2);
    c1.addNode(Id2, 0);
    c2.setVector(c1.getVector());

    Assert.assertEquals(c1.getVector(), c2.getVector());
  }