NodeJS | Jest | Factory Girl | Faker: Faker generating the same values

Question

I'm developing a Node.js API and now I'm creating the tests using supertest for all the routes.

I found the best practice is to use the factory-girl and the faker to generate random values for the models.

Knowing that, I created my factory.js:

  import faker from 'faker/locale/pt_BR';
  import { factory } from 'factory-girl';

  import User from '../src/app/models/User';

  factory.define('User', User, {
    name: faker.name.findName(),
    email: faker.internet.email(),
    password: faker.internet.password(),
  });

  export default factory;

Its works beautiful when I executed one time:

  it('should be able to register', async () => {
    const user = await factory.attrs('User');

    const response = await request(app)
      .post('/users')
      .send(user);

    expect(response.body).toHaveProperty('id');
  });

The line const user = await factory.attrs('User'); returns the following model:

  {
    name: 'Sra. Dalila Pereira',
    email: '[email protected]',
    password: 'zhpMclO9KwWfhlt'
  }

But if I call the same instruction two times, the models will be equals:

  it('should return all users', async () => {
    const user1 = await factory.attrs('User');

    await request(app)
      .post('/users')
      .send(user1);

    const user2 = await factory.attrs('User');

    await request(app)
      .post('/users')
      .send(user2);

    const response = await request(app)
      .get('/users')
      .set('Authorization', `Bearer ${token}`);

    expect(response.status).toBe(200);
  });

Model: user1

   {
     name: 'Salvador Costa',
     email: '[email protected]',
     password: 'Q4EfvNJv9zulONR'
   }

Model: user2

   {
     name: 'Salvador Costa',
     email: '[email protected]',
     password: 'Q4EfvNJv9zulONR'
   }

So when the second post is called an error occurs because the user already exists.

Do you know what can I do to solve this problem?

Thanks

Answer 1

The documentation provides this example:

// Using objects as initializer
factory.define('product', Product, {
  // use sequences to generate values sequentially
  id: factory.sequence('Product.id', (n) => `product_${n}`),

  // use functions to compute some complex value
  launchDate: () => new Date(),
  // ...
})

The launchDate field is being calculated per-call.

The same should hold true for faker. In order to guarantee a fresh value every time, try providing an arrow function.

factory.define('User', User, {
  name: () => faker.name.findName(),
  email: () => faker.internet.email(),
  password: () => faker.internet.password(),
});