private static void validateSingleEntry(Object key, String value) {
    try {
      Region r = cache.getRegion(SEPARATOR + REGION_NAME);
      assertEquals(value, r.getEntry(key).getValue());
    } catch (Exception ex) {
      Assert.fail("failed while validateSingleEntry()", ex);
    }
  }
unregister a key for a particular client in the server

@param clientId the client's ID
@param key the key it's no longer interest in
geode-core/src/distributedTest/java/org/apache/geode/internal/cache/tier/sockets/InterestListDUnitTest.java