private long runSnapshot(final AbstractMemStore hmc) throws UnexpectedStateException {
    // Save off old state.
    int oldHistorySize = hmc.getSnapshot().getCellsCount();
    MemStoreSnapshot snapshot = hmc.snapshot();
    // Make some assertions about what just happened.
    assertTrue("History size has not increased",
      oldHistorySize < hmc.getSnapshot().getCellsCount());
    long t = memstore.timeOfOldestEdit();
    assertTrue("Time of oldest edit is not Long.MAX_VALUE", t == Long.MAX_VALUE);
    hmc.clearSnapshot(snapshot.getId());
    return t;
  }
Adds {@link #ROW_COUNT} rows and {@link #QUALIFIER_COUNT}
@param hmc Instance to add rows to.
@return How many rows we added.
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestDefaultMemStore.java