public function testHeaders()
{
$headers = new Headers();
$this->assertTrue($headers instanceof \IteratorAggregate);
$this->assertTrue($headers instanceof \Traversable);
$this->assertTrue($headers instanceof \ArrayAccess);
$this->assertTrue($headers instanceof \Serializable);
$this->assertTrue($headers instanceof \Countable);
$client = new Client();
$client->setDefaultRequestHeaders($headers);
$this->assertTrue($headers === $client->getDefaultRequestHeaderds());
// Default initialization
$client = new Client();
$headers = $client->getDefaultRequestHeaderds();
$this->assertTrue($headers instanceof Headers);
$this->assertTrue($headers === $client->getDefaultRequestHeaderds());
$this->assertArrayHasKey('User-Agent', $headers);
$this->assertEquals('fb-php-ads-' . Api::VERSION, $headers['User-Agent']);
}
