How do you mock?

[DHFW]

For unit testing and mocking of database calls I use the following:

modelsSpy = jest.spyOn(models.CourseParticipation, 'query');
      modelsSpy.mockReturnValue({
        eager: (): any => {
          return {
            findById: (queryObject: any): Partial<CourseParticipation> => {
              return {
                PersonID: 1,
                SomeOtherKeyID: 1,
                Course: {
                  CourseCode: '1234',
                  SpecialtyID: 123,
                  Title: 'Test course',
                  Sessions: [
                    {
                      Date: new Date(2019, 0, 1), // Local time
                      Begintime: new Date(1970, 0, 1, 13, 0, 0, 0), // Local time
                    },
                  ],
                },
              };
            },
          };
        },
        where: (): any => {
          return {
            patch: (): number => {
              return 1;
            },
          };
        },
      });

This works pretty well for me (ObjectionJS version: 1.6.8) with Jest 24. I wonder what your code looks like? We don't have so much help from TypeScript here (using everything as any because the models have so many properties and methods), so any ;) suggestions are welcome!

[koskimas]

You can use the resolve method to skip the db query and mock the db result.

[DHFW]

@koskimas Thanks for the quick response. However, do you have an example how to implement this in a simple unit test? How do I go about this when I want to spy/mock on just say one findById request?

[will-hang]

Yeah, I'd love to +1 @DHFW's most recent comment. Specifically,

if I already have calls to Model.query().select().join() in my server code, is there any cleaner way to mock the entire call in some unit test? Or will @DHFW's first post have to suffice?

[devinivy]

You can override the model's query() method so that it returns a query builder calling resolve() with whatever value you like. There's some more info about this in the docs here: https://vincit.github.io/objection.js/recipes/custom-query-builder.html#custom-query-builder-extending-the-query-builder

[will-hang]

Thanks @devinivy. Does this mean that I either need to go and edit my DB code so that it calls the resolve() function? As in, there is no in-place mock? Or, are you suggesting that I can completely mock out query() with resolve() and everything will be fine?

The reason I'd like to clarify is that query() is often the first in a chain of calls. Mocking query() to return the result of resolve() instead, when there are still chained calls after query(), seems like it will break anything chained onto query().

[devinivy]

It should work just fine without modifying any application code! As the docs show, queryBuilder.resolve() returns queryBuilder, so you can keep chaining :) https://vincit.github.io/objection.js/api/query-builder/other-methods.html#resolve

[will-hang]

Oh damn! Amazing! Thanks so much for pointing that out. This is a huge plus for the community because this just makes server testing so much easier now. Thank you all!

[aalimovs]

For anyone stumbling upon this from hapi/hapipal/schwifty land, here's an example for a route handler:

// route handler
const { Person } = request.models(true);
const person = await Person.query().findById(request.params.id);

// test with stub
import { QueryBuilder } from 'objection';

const { Person } = server.models(true); // or import Person from '../wherever/models/Person';

Sinon.stub(server.models(true), 'Person').value({
    query: () => QueryBuilder.forClass(Person).resolve({ id: 111 }),
});

[lucasrcosta]

I have found that mock-knex offers the most complete experience for mocking and asserting the queries. :orange_circle: :orange_circle:

[richardweaver]

@lucasrcosta How are you injecting the mock-knex instance? I can't figure it out.