public void testToString_addValueWithNullValue() {
    final String result =
        MoreObjects.toStringHelper(new TestClass())
            .addValue(null)
            .addValue("Hello")
            .addValue(null)
            .toString();
    final String expected = "TestClass{null, Hello, null}";

    assertEquals(expected, result);
  }

    public ToStringHelper addValue(@CheckForNull Object value) {
      return addHolder(value);
    }

    /**
     * Adds an unnamed value to the formatted output.
     *
     * <p>It is strongly encouraged to use {@link #add(String, boolean)} instead and give value a
     * readable name.
     *
     * @since 18.0 (since 11.0 as {@code Objects.ToStringHelper.addValue()}).
     */
    @CanIgnoreReturnValue