@Override
      public List<HStoreFile> next() {
        count += 1;
        ArrayList<HStoreFile> files = new ArrayList<>(NUM_FILES_GEN);
        for (int i = 0; i < NUM_FILES_GEN; i++) {
          files.add(createMockStoreFile(FILESIZE));
        }
        return files;
      }
How many mb's mock storefiles should be.
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/compactions/ConstantSizeFileListGenerator.java