private void populateRRRegion() {
    Region<String, Integer> region = CacheFactory.getAnyInstance().getRegion(REPLICATE_REGION_NAME);
    assertThat(region).isNotNull();

    final HashSet<String> testKeys = new HashSet<>();
    for (int i = 17 * 3; i > 0; i--) {
      testKeys.add("execKey-" + i);
    }
    int j = 0;
    for (final String testKey : testKeys) {
      region.put(testKey, j++);
    }

  }
Dunit Test to validate OnRegion function execution with REST APIs

@since GemFire 8.0
geode-assembly/src/distributedTest/java/org/apache/geode/rest/internal/web/controllers/RestAPIOnRegionFunctionExecutionDUnitTest.java