public void SHUpdateTest() {
      callback_count = 0;
      int spi = SecurityPolicy.DefaultSPI;
      MockSender sender1 = new MockSender(null, null, null, 2);
      MockSender sender2 = new MockSender(null, null, null, 2);
      SecurityAssociation sa1 = new SecurityAssociation(sender1, spi); 
      sa1.StateChange += StateChange;
      sender2.Receiver = sa1;
      MockDataHandler mdh1 = new MockDataHandler();
      sa1.Subscribe(mdh1, null);
      SecurityAssociation sa2 = new SecurityAssociation(sender2, spi); 
      sender1.Receiver = sa2;
      MockDataHandler mdh2 = new MockDataHandler();
      sa2.Subscribe(mdh2, null);

      Setup(ref sa1, ref sa2);

      sa1.RequestUpdate += Callback;
      sa2.RequestUpdate += Callback;

      byte[] b = null;
      Random rand = new Random();
      MemBlock mb = null;

      int current_epoch = sa1.CurrentEpoch;
      for(int i = 0; i < 80; i++) {
        b = new byte[128];
        rand.NextBytes(b);
        mb = MemBlock.Reference(b);
        sa1.Send(mb);
        Assert.IsTrue(mdh2.Contains(mb), "Contains" + i);
        if(i % 20 == 0 && i != 0) {
          Assert.AreEqual(callback_count, 1, "Callback count " + i);
          callback_count = 0;
          Thread.Sleep(SecurityAssociation.TIMEOUT * 2 + 5);
          Setup(ref sa1, ref sa2);
        } else {
          if(i % 20 == 1 && i != 1) {
            Assert.IsFalse(current_epoch == sa1.CurrentEpoch, "Current epoch " + i);
            current_epoch = sa1.CurrentEpoch;
          }
          Assert.AreEqual(current_epoch, sa1.CurrentEpoch, "Current epoch " + i);
        }
      }
    }
    public void Test() {
      int spi = SecurityPolicy.DefaultSPI;
      MockSender sender1 = new MockSender(null, null, null, 2);
      MockSender sender2 = new MockSender(null, null, null, 2);
      SecurityAssociation sa1 = new SecurityAssociation(sender1, spi); 
      sa1.StateChange += StateChange;
      sender2.Receiver = sa1;
      MockDataHandler mdh1 = new MockDataHandler();
      sa1.Subscribe(mdh1, null);
      SecurityAssociation sa2 = new SecurityAssociation(sender2, spi); 
      sender1.Receiver = sa2;
      MockDataHandler mdh2 = new MockDataHandler();
      sa2.Subscribe(mdh2, null);

      byte[] b = null;
      Random rand = new Random();
      MemBlock mb = null;

      int current_epoch = sa1.CurrentEpoch;
      for(int i = 0; i < 5; i++) {
        Thread.Sleep(SecurityAssociation.TIMEOUT * 2 + 5);
        Setup(ref sa1, ref sa2);

        b = new byte[128];
        rand.NextBytes(b);
        mb = MemBlock.Reference(b);
        sa1.Send(mb);
        Assert.IsTrue(mdh2.Contains(mb), "Contains" + i);
        Assert.AreEqual(state, sa1.State, "State == Active" + i);
        Assert.IsFalse(current_epoch == sa1.CurrentEpoch, "Current epoch " + i);
        current_epoch = sa1.CurrentEpoch;
      }

      sa1.GarbageCollect();
      sa1.GarbageCollect();
      b = new byte[128];
      rand.NextBytes(b);
      mb = MemBlock.Reference(b);
      try {
        sa1.Send(mb);
      } catch {}
      Assert.IsTrue(!mdh2.Contains(mb), "Failed!");
      Assert.AreEqual(state, sa1.State, "State == Failed");
    }