@After
  public void tearDown() throws IOException {
    if (region != null) {
      HBaseTestingUtil.closeRegionAndWAL(region);
    }

    // We have to re-set the lazy seek flag back to the default so that other
    // unit tests are not affected.
    StoreScanner.enableLazySeekGlobally(StoreScanner.LAZY_SEEK_ENABLED_BY_DEFAULT);
  }
Disable this when this test fails hopelessly and you need to debug a simpler case.
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestSeekOptimizations.java