assertThrows(IndexOutOfBoundsException.class, () -> checkElementIndex(-1, 1));
    assertThat(expected).hasMessageThat().isEqualTo("index (-1) must not be negative");
  }

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