private static void assertVersion(GemFireCache cache, short ordinal) {
    DistributedSystem system = cache.getDistributedSystem();
    int thisOrdinal =
        ((InternalDistributedMember) system.getDistributedMember()).getVersion()
            .ordinal();
    if (ordinal != thisOrdinal) {
      throw new Error(
          "Version ordinal:" + thisOrdinal + " was not the expected ordinal of:" + ordinal);
    }
  }
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