testers.add(ListLastIndexOfTester.class);
    testers.add(ListListIteratorTester.class);
    testers.add(ListRemoveAllTester.class);
    testers.add(ListRemoveAtIndexTester.class);
    testers.add(ListRemoveTester.class);
    testers.add(ListReplaceAllTester.class);
    testers.add(ListRetainAllTester.class);
    testers.add(ListSetTester.class);
    testers.add(ListSubListTester.class);
    testers.add(ListToArrayTester.class);

    @CanIgnoreReturnValue
    @Override
    public Builder<E> add(E element) {
      contents.add(checkNotNull(element));
      return this;
    }

    @CanIgnoreReturnValue
    @Override
    public Builder<E> add(E... elements) {
      checkNotNull(elements); // for GWT
      contents.ensureCapacity(contents.size() + elements.length);
      super.add(elements);
      return this;
    }

    assertThat(builder.build()).containsExactly("a", "b").inOrder();
    builder.add("c", "d");
    assertThat(builder.build()).containsExactly("a", "b", "c", "d").inOrder();
  }

  public void testBuilderWithDuplicateElements() {
    ImmutableSet<String> set =
        this.<String>builder()
            .add("a")
            .add("a", "a")
            .add("a", "a", "a")

        TestCorsHandler handler3 = new TestCorsHandler("handler3");

        // Execute
        corsHandlerFactory.add(origin1, handler1);
        corsHandlerFactory.add(origin2, handler2);
        corsHandlerFactory.add(origin3, handler3);

        // Verify
        assertEquals(handler1, corsHandlerFactory.get(origin1));
        assertEquals(handler2, corsHandlerFactory.get(origin2));

        List<ColumnInfo> ls = newArrayList();
        ls.add(columnCreatedBy());
        ls.add(columnCreatedTime());
        ls.add(columnFileConfigId());
        ls.add(columnHostname());
        ls.add(columnParameters());
        ls.add(columnPassword());
        ls.add(columnPort());
        ls.add(columnProtocolScheme());
        ls.add(columnUpdatedBy());
        ls.add(columnUpdatedTime());
        ls.add(columnUsername());

        }
    }

    // Test add method with null dataStore
    public void test_add_nullDataStore() {
        try {
            dataStoreFactory.add("testName", null);
            fail("Should throw IllegalArgumentException");
        } catch (IllegalArgumentException e) {
            assertEquals("name or dataStore is null.", e.getMessage());
        }
    }

    // Test add method with both null parameters

    Set<Set<Integer>> expected = new HashSet<>();
    expected.add(ImmutableSet.<Integer>of());
    expected.add(ImmutableSet.of(1));
    expected.add(ImmutableSet.of(2));
    expected.add(ImmutableSet.of(3));
    expected.add(ImmutableSet.of(1, 2));
    expected.add(ImmutableSet.of(1, 3));
    expected.add(ImmutableSet.of(2, 3));
    expected.add(ImmutableSet.of(1, 2, 3));

   * // Returns "ClassName{x=1}"
   * MoreObjects.toStringHelper(this)
   *     .add("x", 1)
   *     .toString();
   *
   * // Returns "MyObject{x=1}"
   * MoreObjects.toStringHelper("MyObject")
   *     .add("x", 1)
   *     .toString();
   *
   * // Returns "ClassName{x=1, y=foo}"
   * MoreObjects.toStringHelper(this)
   *     .add("x", 1)
   *     .add("y", "foo")
   *     .toString();
   *
   * // Returns "ClassName{x=1}"

    testers.add(CollectionSerializationEqualTester.class);
    testers.add(MultisetAddTester.class);
    testers.add(MultisetContainsTester.class);
    testers.add(MultisetCountTester.class);
    testers.add(MultisetElementSetTester.class);
    testers.add(MultisetEqualsTester.class);
    testers.add(MultisetForEachEntryTester.class);
    testers.add(MultisetReadsTester.class);

        doc1.put("title", "Doc1");
        Map<String, Object> doc2 = new HashMap<>();
        doc2.put("title", "Doc2");
        documentList.add(doc1);
        documentList.add(doc2);
        documentList.add(doc1); // duplicate

        QueryResponseList qrList = new QueryResponseList(documentList, 0, 10, 0);

        assertEquals(0, qrList.indexOf(doc1));