public function testCacheControlDirectiveAccessors()
 {
     $bag = new HeaderBag();
     $bag->addCacheControlDirective('public');
     $this->assertTrue($bag->hasCacheControlDirective('public'));
     $this->assertTrue($bag->getCacheControlDirective('public'));
     $this->assertEquals('public', $bag->get('cache-control'));
     $bag->addCacheControlDirective('max-age', 10);
     $this->assertTrue($bag->hasCacheControlDirective('max-age'));
     $this->assertEquals(10, $bag->getCacheControlDirective('max-age'));
     $this->assertEquals('max-age=10, public', $bag->get('cache-control'));
     $bag->removeCacheControlDirective('max-age');
     $this->assertFalse($bag->hasCacheControlDirective('max-age'));
 }