@Test
  public void testRegionWithNullServerName() throws Exception {
    RegionLocator regionLocator =
      mockRegionLocator(null, Collections.singletonList("someBigRegion"));
    Admin admin = mockAdmin(mockRegion("someBigRegion", Integer.MAX_VALUE, Integer.MAX_VALUE));
    RegionSizeCalculator calculator = new RegionSizeCalculator(regionLocator, admin);
    assertEquals(0, calculator.getRegionSize(Bytes.toBytes("someBigRegion")));
  }
When calculator is disabled, it should return 0 for each request.
hbase-mapreduce/src/test/java/org/apache/hadoop/hbase/mapreduce/TestRegionSizeCalculator.java