public static void testConvertToJSON(BlockCache toBeTested) {
    try {
      String json = BlockCacheUtil.toJSON(toBeTested);
      assertNotNull(json);
    } catch (Exception e) {
      fail("conversion to JSON should not fail, exception is:" + e);
    }
  }
Just checks if heapsize grows when something is cached, and gets smaller when the same object
is evicted
hbase-server/src/test/java/org/apache/hadoop/hbase/io/hfile/CacheTestUtils.java