assertInvariants(map);
      try {
        iterator.remove();
        fail("Expected IllegalStateException.");
      } catch (IllegalStateException expected) {
      }
    } else {
      iterator.next();
      try {
        iterator.remove();
        fail("Expected UnsupportedOperationException.");
      } catch (UnsupportedOperationException expected) {
      }
    }

	if err == nil {
		t.Fatal("Expected for Rlock to fail")
	}

	_, err = lkClient.Lock(context.Background(), dsync.LockArgs{})
	if err == nil {
		t.Fatal("Expected for Lock to fail")
	}

	_, err = lkClient.RUnlock(context.Background(), dsync.LockArgs{})
	if err == nil {
		t.Fatal("Expected for RUnlock to fail")
	}

	_, err = lkClient.Unlock(context.Background(), dsync.LockArgs{})

    filtered.put("a", 1);
    filtered.put("b", 2);
    assertEquals(ImmutableMap.of("a", 1, "b", 2), filtered);

    try {
      filtered.put("yyy", 3);
      fail();
    } catch (IllegalArgumentException expected) {
    }
  }

  public void testFilteredKeysIllegalPutAll() {
    Map<String, Integer> unfiltered = createUnfiltered();

    filtered.put("a", 1);
    filtered.put("b", 2);
    assertEquals(ImmutableMap.of("a", 1, "b", 2), filtered);

    try {
      filtered.put("yyy", 3);
      fail();
    } catch (IllegalArgumentException expected) {
    }
  }

  public void testFilteredKeysIllegalPutAll() {
    Map<String, Integer> unfiltered = createUnfiltered();

    future.cancel(true);
    try {
      getUnchecked(future);
      fail();
    } catch (CancellationException expected) {
    }
  }

  public void testGetUnchecked_ExecutionExceptionChecked() {
    try {
      getUnchecked(FAILED_FUTURE_CHECKED_EXCEPTION);
      fail();
    } catch (UncheckedExecutionException expected) {
      assertEquals(CHECKED_EXCEPTION, expected.getCause());

      put(e3());
      iterator.next();
      fail("Expected ConcurrentModificationException");
    } catch (ConcurrentModificationException expected) {
      // success
    }
  }

  @MapFeature.Require(absent = SUPPORTS_PUT)
  public void testPut_unsupportedNotPresent() {
    try {
      put(e3());
      fail("put(notPresent, value) should throw");

      try {
        testInstance.clear();
        fail();
      } catch (UnsupportedOperationException e) {
        // success
      }
    }
  }

  public final void testPut() {
    for (Table<Character, Integer, String> testInstance : getTestInstances()) {
      try {
        testInstance.put('a', 1, "blah");
        fail();
      } catch (UnsupportedOperationException e) {
        // success

	}
	metrics := globalTierMetrics.Report()
	var succ, fail float64
	for _, metric := range metrics {
		switch metric.Description.Name {
		case tierRequestsSuccess:
			succ += metric.Value
		case tierRequestsFailure:
			fail += metric.Value
		}
	}
	if int(succ) != expSuccess {
		t.Fatalf("Expected %d successes but got %f", expSuccess, succ)
	}
	if int(fail) != expFailure {

    Iterator<Object> empty = new EmptyAbstractSequentialIterator<>();
    assertFalse(empty.hasNext());
    try {
      empty.next();
      fail();
    } catch (NoSuchElementException expected) {
    }
    try {
      empty.remove();
      fail();
    } catch (UnsupportedOperationException expected) {
    }
  }

  public void testBroken() {

    try {
      diff1.entriesInCommon().put(7, "x");
      fail();
    } catch (UnsupportedOperationException expected) {
    }
    try {
      diff1.entriesOnlyOnLeft().put(7, "x");
      fail();
    } catch (UnsupportedOperationException expected) {
    }
    try {
      diff1.entriesOnlyOnRight().put(7, "x");
      fail();
    } catch (UnsupportedOperationException expected) {
    }
  }