void () { Collection<String> errors = new TreeSet<>(); TipAndTrickBean[] tips = TipAndTrickBean.EP_NAME.getExtensions(); assertNotEmpty(Arrays.asList(tips)); Set<String> visited = new LinkedHashSet<>(); for (TipAndTrickBean tip : tips) { if (!visited.add(tip.fileName)) { errors.add(tip.fileName); } } assertEquals("The following tip files are registered more than once:\n" + StringUtil.join(errors, "\n"), 0, errors.size()); }