public function testGetCredentials()
 {
     $login = '******';
     $password = '******';
     $c = new Client();
     $c->setLogin($login);
     $c->setPassword($password);
     $expected = base64_encode(sprintf('%s:%s', $c->getLogin(), $c->getPassword()));
     $this->assertEquals($expected, $c->getCredentials(), "Getter doesn't work as expected");
 }