private void createMockRegionExtension(final String regionName, final String value) {
    CommandStringBuilder csb =
        new CommandStringBuilder(MockExtensionCommands.CREATE_MOCK_REGION_EXTENSION);
    csb.addOption(MockExtensionCommands.OPTION_REGION_NAME, regionName);
    csb.addOption(MockExtensionCommands.OPTION_VALUE, value);
    gfsh.executeAndAssertThat(csb.toString()).statusIsSuccess();
  }
Tests for {@link Extension}, {@link Extensible}, {@link XmlParser}, {@link XmlGenerator},
{@link XmlEntity} as it applies to Extensions. Asserts that Mock Extension is created and
destroyed on region and cache.

@since GemFire 8.1
geode-core/src/distributedTest/java/org/apache/geode/internal/cache/extension/ExtensionClusterConfigurationDUnitTest.java