### Question:
UrlButton extends Button { private UrlButton(String text) { super(text); } private  UrlButton(String text); static final UrlButton styledUrlButton(String text, String url, FontAwesomeIcon icon); static final UrlButton urlButton(String text, String url, FontAwesomeIcon icon, String... style);  }### Answer:
@Test(expected = IllegalArgumentException.class) public void nullUrl() { UrlButton.urlButton("Chuck", null, FontAwesomeIcon.ADN); }
@Test(expected = IllegalArgumentException.class) public void emptyUrl() { UrlButton.urlButton("Chuck", "", FontAwesomeIcon.ADN); }