private CacheSerializableRunnable invokeAssertEntriesCorrect(final String regionName,
      final int start, final int end) {
    return new CacheSerializableRunnable("execute: assertEntriesCorrect") {
      @Override
      public void run2() {
        try {
          assertEntriesCorrect(RollingUpgrade2DUnitTestBase.cache, regionName, start, end);
        } catch (Exception e) {
          fail("Error asserting equals", e);
        }
      }
    };
  }
This test starts up multiple servers from the current code base and multiple servers from the
old version and executes puts and gets on a new server and old server and verifies that the
results are present. Note that the puts have overlapping region keys just to test new puts and
replaces
geode-core/src/upgradeTest/java/org/apache/geode/internal/cache/rollingupgrade/RollingUpgrade2DUnitTestBase.java