@Override
  public OptionalLong getMinimumTimestamp() {
    return timeRangeTracker == null
      ? OptionalLong.empty()
      : OptionalLong.of(timeRangeTracker.getMin());
  }
A mock used so our tests don't deal with actual StoreFiles
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/MockHStoreFile.java