public function testRenderBlockOptimizer() {
$env = new Twig_Environment(new Twig_Loader_String(), array(
'cache' => false,
'autoescape' => false,
));
$env
->addExtension(new Twig_Extension_Optimizer());
$stream = $env
->parse($env
->tokenize('{{ block("foo") }}', 'index'));
$node = $stream
->getNode('body')
->getNode(0);
$this
->assertEquals('Twig_Node_Expression_BlockReference', get_class($node));
$this
->assertTrue($node
->getAttribute('output'));
}