Having trouble figuring out how to mock Model with Jest

I’m having trouble figuring out how I would mock Agreement.query().where().where() in a proper way. Here is the code with two models, Agreement and AgreementHistory.

const { Model, snakeCaseMappers } = require('objection');
const knex = require('knex')({
  client: 'postgresql',
  connection: process.env.MY_CONNECTION_STRING
});
Model.knex(knex);

class Agreement extends Model {
  static get tableName() {
    return 'agreement';
  }

  static get idColumn() {
    return 'agreement_id';
  }

  static get columnNameMappers() {
    return snakeCaseMappers();
  }
}

const getAgreements = async (filterOptions = {}) => {
  const { customerId, status } = filterOptions;
  const query = Agreement
    .query()
    .where({ customer_id: parseInt(customerId) });

  if (status) {
    query.where({ status: status });
  }

  return await query;
};

module.exports =  {
  getAgreements
};

/__mocks__/agreement.js

const mock = {
  query: jest.fn().mockReturnThis(),
  where: jest.fn().mockImplementation(() => {
    return {
      where: jest.fn().mockReturnValue('Hello World')
    }
  })
};
module.exports = mock;

The above mock could get ugly really fast if there are n-many where() calls. It’s a bit confusing because Objection allows the nice chaining syntax, but I am insure how I would create the mocks in Jest to support this.

Test File.

jest.mock('../models/agreement');
const Agreement = require('../models/agreement');

const repository = require('../agreementRepository');
  describe('getAgreements', () => {
    it.only('should allow filtering by customerId and status (if provided)', async () => {
      const results = await repository.getAgreements({ customerId: 555, status: 'Accepted' });
      expect(Agreement.query).toHaveBeenCalled(); // This test passes
      expect(results).toEqual('Hello World'); // This one fails. Error output below
    });
});

Error output from test above

Expected: "Hello World"
Received: {"where": [Function mockConstructor]}

Please let me know if this should be posted in the Jest issues page instead. Thanks.

[koskimas]

@armandAkop You need to mock the prototype of the QueryBuilder class. Jest probably has examples of that

[armandAkop]

We ended up creating a “BaseModel” class which extends Model, then in our mocks we did this

let returnValue = null;

class BaseModel {};

/**
 * Sets return value on thenable module.
 * @param {*} value 
 */
BaseModel.mockReturnValue = (value) => {
    returnValue = value;
};

BaseModel.query = jest.fn().mockReturnThis();
BaseModel.insert = jest.fn().mockReturnThis();
BaseModel.insertGraphAndFetch = jest.fn().mockReturnThis();
BaseModel.insertGraph = jest.fn().mockReturnThis();
BaseModel.returning = jest.fn().mockReturnThis();
BaseModel.where = jest.fn().mockReturnThis();
BaseModel.withGraphFetched = jest.fn().mockReturnThis();
BaseModel.findById = jest.fn().mockReturnThis();
BaseModel.modifiers = jest.fn().mockReturnThis();
BaseModel.orderBy = jest.fn().mockReturnThis();
BaseModel.startTransaction = jest.fn();
BaseModel.then = jest.fn((done) => { done(returnValue); });

module.exports = BaseModel;

And this seemed to work fine for our case.