Is there a way to mock populate for mongoose?

Schema:

const  mongoose = require('mongoose');
const { Schema } = mongoose;

const user = Schema({
    name: String,
    email: String,
    foo: { type: String, ref: 'Foo' },
    created: { type: Date, default: Date.now }
})

const foo = Schema({
    name: String,
    email: String,
    created: { type: Date, default: Date.now }
})

const User = mongoose.model('User', user);
const Foo = mongoose.model('Foo', foo);

module.exports = { User, Foo };

Test:

const mockingoose = require('mockingoose').default;
const { User, Foo } = require('./schema');
describe('test mongoose User model', () => {
  it('should return the doc with findById', async () => {
    const _doc = {
        _id: '507f191e810c19729de860ea',
        name: 'name',
        foo: {
          name: 'bar',
        },
        email: '[e-mail]'
    };
    const _doc2 = {
        _id: '507f191e810c19729de860ea',
        name: 'name2',
        foo: {
          name: 'bar',
        },
        email: '[e-mail]'
    };

    const foo = await Foo.create({name: 'bar'});
    _doc.foo = foo._id;

    mockingoose.User.toReturn(_doc, 'findOne');
    // mockingoose.User.toReturn(_doc2, 'populate');
    const user = await User.findOne({ _id: '507f191e810c19729de860ea'}).populate('foo');
    console.log(user);
    // expect(JSON.parse(JSON.stringify(user))).toMatchObject(_doc);
  });
});

[alonronin]

it is not suppose to populate as it is just a mock, so if you use populate, mock the complete result.

[refextu]

The issue was not to try to populate. @alonronin: the fact is: that there is no way to mock the complete result. When I try to mock the response (see above) the result is:

    { _id: 507f191e810c19729de860ea,
      name: 'name',
      foo: '5bf52e68c3d3c8098cd840b1',
      email: '[e-mail]',
      created: 2018-11-21T10:07:36.290Z }

Even when i try to return _doc2 I’ll have the problem, that I don’t get foo:

    { _id: 507f191e810c19729de860ea,
      name: 'name2',
      email: '[e-mail]',
      created: 2018-11-21T10:10:01.734Z }