VM rollServerToCurrentAndCreateRegion(VM oldServer, RegionShortcut shortcut,
      String regionName, int[] locatorPorts) {
    VM newServer = rollServerToCurrent(oldServer, locatorPorts);
    // recreate region on "rolled" server
    invokeRunnableInVMs(invokeCreateRegion(regionName, shortcut), newServer);
    newServer.invoke(invokeRebalance());
    return newServer;
  }
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