@Test
 public void testJoin1() {
   Stamp aNonNull = StampFactory.declaredNonNull(getType(A.class));
   Stamp b = StampFactory.declared(getType(B.class));
   Stamp bNonNull = StampFactory.declaredNonNull(getType(B.class));
   Assert.assertEquals(bNonNull, join(aNonNull, b));
 }
 @Test
 public void testJoinInterface1() {
   Stamp aNonNull = StampFactory.declaredNonNull(getType(A.class));
   Stamp i = StampFactory.declaredTrusted(getType(I.class));
   Stamp join = join(aNonNull, i);
   Assert.assertTrue(join instanceof ObjectStamp);
   Assert.assertTrue(((ObjectStamp) join).nonNull());
 }