Mock Mongoose

A Package for mocking Mongoose models that can be utilized with any node.js testing library such as Jest, Mocha, and Vitest etc ..

Installation

With NPM:

$ npm i @jazim/mock-mongoose -D

Import the library

const mockify = require('@jazim/mock-mongoose');

Usage

// user.js
const mongoose = require('mongoose');
const { Schema } = mongoose;

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

module.exports = mongoose.model('User', schema);

mockify(Model).toReturn(obj, operation = 'find')

Returns a plain object.

// __tests__/user.test.js
const mockify = require('@jazim/mock-mongoose');

const model = require('./user');

describe('test mongoose User model', () => {
  it('should return the doc with findById', () => {
    const _doc = {
      _id: '507f191e810c19729de860ea',
      name: 'name',
      email: 'name@email.com',
    };

    mockify(model).toReturn(_doc, 'findOne');

    return model.findById({ _id: '507f191e810c19729de860ea' }).then((doc) => {
      expect(JSON.parse(JSON.stringify(doc))).toMatchObject(_doc);
    });
  });

  it('should return the doc with update', () => {
    const _doc = {
      _id: '507f191e810c19729de860ea',
      name: 'name',
      email: 'name@email.com',
    };

    mockify(model).toReturn(_doc, 'update');

    return model
      .update({ name: 'changed' }) // this won't really change anything
      .where({ _id: '507f191e810c19729de860ea' })
      .then((doc) => {
        expect(JSON.parse(JSON.stringify(doc))).toMatchObject(_doc);
      });
  });
});

mockify(Model).toReturn(fn, operation = 'find')

Allows passing a function in order to return the result.

You will be able to inspect the query using the parameter passed to the function. This will be either a Mongoose Query or Aggregate class, depending on your usage.

You can use snapshots to automatically test that the queries sent out are valid.

// __tests__/user.test.js
const mockify = require('@jazim/mock-mongoose');
const model = require('./user');

describe('test mongoose User model', () => {
  it('should return the doc with findById', () => {
    const _doc = {
      _id: '507f191e810c19729de860ea',
      name: 'name',
      email: 'name@email.com',
    };
    const finderMock = (query) => {
      expect(query.getQuery()).toMatchSnapshot('findById query');

      if (query.getQuery()._id === '507f191e810c19729de860ea') {
        return _doc;
      }
    };

    mockify(model).toReturn(finderMock, 'findOne'); // findById is findOne

    return model.findById('507f191e810c19729de860ea').then((doc) => {
      expect(JSON.parse(JSON.stringify(doc))).toMatchObject(_doc);
    });
  });
});

mockify(Model).reset(operation = undefined)

will reset Model mock, if pass an operation, will reset only this operation mock.

it('should reset model mock', () => {
  mockify(model).toReturn({ name: '1' });
  mockify(model).toReturn({ name: '2' }, 'save');

  mockify(model).reset(); // will reset all operations;
  mockify(model).reset('find'); // will reset only find operations;
});

you can also chain mockify#ModelName operations:

mockify(model)
  .toReturn({ name: 'name' })
  .toReturn({ name: 'a name too' }, 'findOne')
  .toReturn({ name: 'another name' }, 'save')
  .reset('find');

mockify.resetAll()

will reset all mocks.

beforeEach(() => {
  mockify.resetAll();
});

Operations available:

• find - for find query
• findOne - for findOne query
• count - for count query (deprecated)
• countDocuments for count query
• estimatedDocumentCount for count collection documents
• distinct - for distinct query
• findOneAndUpdate - for findOneAndUpdate query
• findOneAndRemove - for findOneAndRemove query
• update - for update query (DEPRECATED)
• updateOne - for updateOne query
• updateMany - for updateMany query
• save - for create, and save documents Model.create() or Model.save() or doc.save()
• remove - for remove query (DEPRECATED)
• deleteOne - for deleteOne query
• deleteMany - for deleteMany query
• aggregate - for aggregate framework
• insertMany - for Model.insertMany() bulk insert, can also pass { lean: true, rawResult: true } options.
• orFail - for findOne().orFail() query or similar ones.

Notes

All operations work with exec, promise and callback.

• if you are using Model.create and you don't pass a mock with mockify you'll receive the mongoose created doc (with ObjectId and transformations)

• validations are working as expected.

• the returned document is an instance of mongoose Model.

• deleteOne and updateOne operation returns original mocked object.

• you can simulate Error by passing an Error to mockify:

  mockify(model).toReturn(new Error('My Error'), 'save');
  
  return model
    .create({ name: 'name', email: 'name@email.com' })
    .catch((err) => {
      expect(err.message).toBe('My Error');
    });

• you can mock .populate in your mocked result just be sure to change the Schema's path to appropriate type (eg: Object | Mixed):

  User.schema.path('foreignKey', Object);
  
  const doc = {
    email: 'test@mail.com',
    foreignKey: {
      _id: '5ca4af76384306089c1c30ba',
      name: 'test',
      value: 'test',
    },
    name: 'Name',
    saveCount: 1,
  };
  
  mockify(User).toReturn(doc);
  
  const result = await User.find();
  
  expect(result).toMatchObject(doc);

• no connection is made to the database (mongoose.connect is mock function)

• will work with node 6.4.x. tested with mongoose 4.x and jest 20.x and mocha.

• check tests for more, feel free to fork and contribute.

Recent Changes:

• mockify.ModelName is deprecated, mockify(Model) is the now the recommended usage, with Model being a Mongoose model class.

  Alternatively, you may pass a string with the model name.

• mockify(Model).toReturn((query) => value) can now take also take a function as a parameter.

  The function is called with either a Query or Aggregate object from Mongoose, depending on the request. This allows tests to ensure that proper queries are sent out, and helps with regression testing.