This test fails.

test_tojson.js

var assert = require('assert'),
  mongoose = require('mongoose'),
  Schema = mongoose.Schema,
  connection;
 
 
beforeEach(function(done) {
  connection = mongoose.createConnection('mongodb://localhost/test');
  connection.on('open', function() {
    connection.db.dropDatabase(done);
  });
});
 
afterEach(function(done) {
  connection.db.dropDatabase(function() {
    connection.close(done);
  });
});
 
describe('Document.prototype.toJSON', function() {
  it('should respect schema options', function(done) {
    var userSchema, User, groupSchema, Group;
 
    userSchema = Schema({name: String});
    // includes virtual path when 'toJSON'
    userSchema.set('toJSON', {getters: true});
    userSchema.virtual('hello').get(function() {
      return 'Hello, ' + this.name;
    });
    User = connection.model('User', userSchema);
 
    groupSchema = Schema({
      name: String,
      _users: [{type: Schema.ObjectId, ref: 'User'}]
    });
    // This test succeeds if you remove the following comment out.
    // groupSchema.set('toJSON', {getters: true});
    Group = connection.model('Group', groupSchema);
 
    User.create({name: 'Alice'}, {name: 'Bob'}, function(err, alice, bob) {
      if (err) done(err);
 
      new Group({name: 'mongoose', _users: [alice, bob]}).save(function(err, group) {
        Group.findById(group).populate('_users').exec(function(err, group) {
          assert(group.toJSON()._users[0].hello);
          done(err);
        });
      });
    });
  });
});