public function testRemoveExtension() {
$twig = new Twig_Environment(new Twig_Loader_String());
$twig
->addExtension(new Twig_Tests_EnvironmentTest_Extension());
$twig
->removeExtension('test');
$this
->assertFalse(array_key_exists('test', $twig
->getTags()));
$this
->assertFalse(array_key_exists('foo_filter', $twig
->getFilters()));
$this
->assertFalse(array_key_exists('foo_function', $twig
->getFunctions()));
$this
->assertFalse(array_key_exists('foo_test', $twig
->getTests()));
$this
->assertFalse(array_key_exists('foo_unary', $twig
->getUnaryOperators()));
$this
->assertFalse(array_key_exists('foo_binary', $twig
->getBinaryOperators()));
$this
->assertFalse(array_key_exists('foo_global', $twig
->getGlobals()));
$this
->assertCount(2, $twig
->getNodeVisitors());
}