public function testThirdPartyAuthorization()
 {
     $authorizerEmail = "*****@*****.**";
     $thirdPartyAuth = new PPSubjectAuthorization($authorizerEmail);
     $cred = new PPSignatureCredential("username", "pwd", "signature");
     $cred->setThirdPartyAuthorization($thirdPartyAuth);
     $this->assertEquals($cred->getThirdPartyAuthorization()->getSubject(), $authorizerEmail);
     $accessToken = "atoken";
     $tokenSecret = "asecret";
     $thirdPartyAuth = new PPTokenAuthorization($accessToken, $tokenSecret);
     $cred->setThirdPartyAuthorization($thirdPartyAuth);
     $this->assertEquals($cred->getThirdPartyAuthorization()->getAccessToken(), $accessToken);
     $this->assertEquals($cred->getThirdPartyAuthorization()->getTokenSecret(), $tokenSecret);
 }