@Test
  public void testRegionTooBusyException() {
    List<Throwable> ts = new ArrayList<>(1);
    final String regionName = this.name.getMethodName();
    ts.add(new RegionTooBusyException(regionName));
    List<Row> rows = new ArrayList<>(1);
    rows.add(Mockito.mock(Row.class));
    List<String> hostAndPorts = new ArrayList<>(1);
    hostAndPorts.add("example.com:1234");
    RetriesExhaustedException ree =
      new RetriesExhaustedWithDetailsException(ts, rows, hostAndPorts);
    assertTrue(ree.toString().contains(regionName));
  }
Assert that a RetriesExhaustedException that has RegionTooBusyException outputs region name.
hbase-client/src/test/java/org/apache/hadoop/hbase/client/TestRetriesExhaustedWithDetailsException.java