code: @Test public void shouldBeThreadSafe() throws Exception {
    final SassCssProcessor processor=new SassCssProcessor(){
      @Override protected void onException(    final WroRuntimeException e){
        throw e;
      }
    }
  ;
    final Callable<Void> task=new Callable<Void>(){
      public Void call(){
        try {
          processor.process(new StringReader("#id {.class {color: red;}}"),new StringWriter());
        }
   catch (      final Exception e) {
          throw new RuntimeException(e);
        }
        return null;
      }
    }
  ;
    WroTestUtils.runConcurrently(task);
  }
  