private CachedItem[] generateFixedBlocks(int numBlocks, int size, String pfx) {
    CachedItem[] blocks = new CachedItem[numBlocks];
    for (int i = 0; i < numBlocks; i++) {
      blocks[i] = new CachedItem(pfx + i, size);
    }
    return blocks;
  }
Tests the concurrent LruAdaptiveBlockCache.
<p>
Tests will ensure it grows and shrinks in size properly, evictions run when they're supposed to
and do what they should, and that cached blocks are accessible when expected to be.
hbase-server/src/test/java/org/apache/hadoop/hbase/io/hfile/TestLruAdaptiveBlockCache.java