code: @Test public void testProcessor() throws Exception {
    final Properties properties=new Properties();
    properties.setProperty("prop1","value1");
    properties.setProperty("prop2","value2");
    properties.setProperty("prop3","value3");
    properties.setProperty("prop4","value4");
    final ResourcePreProcessor processor=new PlaceholderProcessor().setPropertiesFactory(WroUtil.simpleObjectFactory(properties));
    final URL url=getClass().getResource("placeholder");
    final File testFolder=new File(url.getFile(),"test");
    final File expectedFolder=new File(url.getFile(),"expected");
    WroTestUtils.compareFromDifferentFoldersByExtension(testFolder,expectedFolder,"css",processor);
  }
  