@Test
  public void testFsReadTimeMetric() throws Exception {
    // write some new puts and flush, as an easy way to ensure the read blocks are not cached
    // so that we go into the fs write code path
    List<Put> puts = createPuts(ROWS, FAMILIES, QUALIFIERS, VALUE);
    TABLE.put(puts);
    TEST_UTIL.flush(TABLE_NAME);
    Scan scan = new Scan();
    scan.setScanMetricsEnabled(true);
    testMetric(scan, ServerSideScanMetrics.FS_READ_TIME_METRIC_NAME, 0, CompareOperator.GREATER);
  }
@return The approximate heap size of a cell in the test table. All cells should have
        approximately the same heap size, so the value is cached to avoid repeating the
        calculation
@throws Exception on unexpected failure
hbase-server/src/test/java/org/apache/hadoop/hbase/TestServerSideScanMetricsFromClientSide.java