assertEquals(1, checkElementIndex(1, 2));
  }

  public void testCheckElementIndex_badSize() {
    assertThrows(IllegalArgumentException.class, () -> checkElementIndex(1, -1));
  }

  public void testCheckElementIndex_negative() {
    IndexOutOfBoundsException expected =
        assertThrows(IndexOutOfBoundsException.class, () -> checkElementIndex(-1, 1));