@Test(expected = QuorumException.class)
 public void testGetAndReplaceOperationThrowsExceptionWhenQuorumSizeNotMet() {
   cache4.getAndReplace(1, "");
 }
 @Test
 public void testGetAndReplaceOperationSuccessfulWhenQuorumSizeMet() {
   cache1.getAndReplace(1, "");
 }