code: @Test public void shouldBeThreadSafe() throws Exception {
    final CssLintProcessor lessCss=new CssLintProcessor(){
      @Override protected void onCssLintException(    final CssLintException e,    final Resource resource){
        throw e;
      }
    }
  ;
    final Callable<Void> task=new Callable<Void>(){
      @Override public Void call(){
        try {
          lessCss.process(new StringReader(createValidCss()),new StringWriter());
        }
   catch (      final Exception e) {
          throw new RuntimeException(e);
        }
        return null;
      }
    }
  ;
    WroTestUtils.runConcurrently(task);
  }
  