public function testCacheControlDirectiveParsing()
 {
     $bag = new HeaderBag(array('cache-control' => 'public, max-age=10'));
     $this->assertTrue($bag->hasCacheControlDirective('public'));
     $this->assertTrue($bag->getCacheControlDirective('public'));
     $this->assertTrue($bag->hasCacheControlDirective('max-age'));
     $this->assertEquals(10, $bag->getCacheControlDirective('max-age'));
     $bag->addCacheControlDirective('s-maxage', 100);
     $this->assertEquals('max-age=10, public, s-maxage=100', $bag->get('cache-control'));
 }