topic: function() {
   return code(function(client, redirectURI, user, scope, ares, done) {
     if (client.id == 'c123' && redirectURI == 'http://example.com/auth/other/callback' && user.id == 'u123' && ares.scope == 'foo') {
       return done(null, 'xyz');
     } else {
       return done(new Error('something is wrong'));
     }
   });
 },
 topic: function() {
   return code(function() {});
 },
 assert.throws(function() { code() });
 topic: function() {
   return code(function(client, redirectURI, user, scope, done) {
     return done(null, 'xyz');
   });
 },
 topic: function() {
   return code(function(client, redirectURI, user, scope, done) {
     return done(new Error('something went wrong'))
   });
 },
 topic: function() {
   return code(function(client, redirectURI, user, scope, done) {
     return done(new Error('should not be called'));
   });
 },
 topic: function() {
   return code({ scopeSeparator: [' ', ','] }, function() {});
 },