### Question:
DefaultIconRenderer implements IconRenderer { @Override public void use(IconSet iconSet) throws IconException { if (iconSet == null) { throw new IconException("The icon set is null", null); } if (!StringUtils.isBlank(iconSet.getCss())) { activeCSS(iconSet); } if (!StringUtils.isBlank(iconSet.getSsx())) { activeSSX(iconSet); } if (!StringUtils.isBlank(iconSet.getJsx())) { activeJSX(iconSet); } }  @Override String render(String iconName, IconSet iconSet); @Override String renderHTML(String iconName, IconSet iconSet); @Override String render(String iconName, IconSet iconSet, String renderer); @Override void use(IconSet iconSet);  }### Answer:
@Test public void useWithIconSetNull() throws Exception { assertThrows(IconException.class, () -> iconRenderer.use(null)); }