DotsUnited\BundleFu\Filter\CallbackFilter::filterFile PHP Method

    public function filterFile($content, $file, \SplFileInfo $fileInfo, $bundleUrl, $bundlePath)
    {
        if (null === $this->callbackFile) {
            return $content;
        }
        return call_user_func($this->callbackFile, $content, $file, $fileInfo, $bundleUrl, $bundlePath);
    }

 public function testNullCallbacks()
 {
     $filter = new CallbackFilter();
     $value = "foo";
     $this->assertEquals($value, $filter->filter($value));
     $this->assertEquals($value, $filter->filterFile($value, '/js/js_1.js', new \SplFileInfo(__DIR__ . '/_files/js/js_1.js'), null, null));
 }