@Test
  public void testOffsetProducesPositiveOutput() {
    // This number is picked because it produces negative output if the values isn't ensured to be
    // positive. See HBASE-18757 for more information.
    long testValue = 549888460800L;
    BucketEntry bucketEntry = new BucketEntry(testValue, 10, 10, 10L, true, (entry) -> {
      return ByteBuffAllocator.NONE;
    }, ByteBuffAllocator.HEAP);
    assertEquals(testValue, bucketEntry.offset());
  }
<pre>
The asserts here before HBASE-21957 are:
assertEquals(1L, cache.getBlockCount());
assertTrue(cache.getCurrentSize() > 0L);
assertTrue("We should have a block!", cache.iterator().hasNext());

The asserts here after HBASE-21957 are:
assertEquals(0, cache.getBlockCount());
assertEquals(cache.getCurrentSize(), 0L);

I think the asserts before HBASE-21957 is more reasonable,because
{@link BucketCache#evictBlock} should only evict the {@link BucketEntry}
it had seen, and newly added Block after the {@link BucketEntry}
it had seen should not be evicted.
</pre>
hbase-server/src/test/java/org/apache/hadoop/hbase/io/hfile/bucket/TestBucketCache.java