validate() public method

public validate ( )
 /**
  * @test
  */
 public function testValidatepwd()
 {
     $this->setExpectedException('PayPal\\Exception\\PPMissingCredentialException');
     $cred = new PPSignatureCredential("platfo_1255077030_biz_api1.gmail.com", "", "Abg0gYcQyxQvnf2HDJkKtA-p6pqhA1k-KTYE0Gcy1diujFio4io5Vqjf");
     $cred->validate();
 }