assertThrows(
        NullPointerException.class,
        () -> equalsTester.addEqualityGroup(reference, equalObject1, null));
  }

  /** Test adding null equal object yields error */
  public void testAddNullEqualObject() {
    assertThrows(
        NullPointerException.class,
        () -> equalsTester.addEqualityGroup(reference, (Object[]) null));
  }

  /**