private void registerInterest(Object keys, String regEx) {
    Region<Object, Object> region = clientCache().getRegion(regionName);
    if (keys == null && regEx == null) {
      region.registerInterest("ALL_KEYS");
    } else if (keys != null) {
      region.registerInterest(keys);
      region.registerInterest("UNKNOWN_KEY");
    } else {
      region.registerInterestRegex(regEx);
    }
  }
Functional distributed tests for Register Interest with KEYS_VALUES policy.

<p>
TRAC #43684: Register interest with policy KEYS_VALUES is inefficient
geode-core/src/distributedTest/java/org/apache/geode/internal/cache/partitioned/RegisterInterestKeysValuesDistributedTest.java