code: @Test public void shouldBeThreadSafe() throws Exception {
    factory=new JsonModelFactory(){
      @Override protected InputStream getModelResourceAsStream() throws IOException {
        return TestGroovyModelFactory.class.getResourceAsStream("wro.json");
      }
    }
  ;
    WroTestUtils.init(factory);
    final WroModel expected=factory.create();
    WroTestUtils.runConcurrently(new Callable<Void>(){
      @Override public Void call() throws Exception {
        Assert.assertEquals(expected,factory.create());
        return null;
      }
    }
  ,10);
  }
  