A way to mock service methods/actions ?

[johanlelan]

Is there a way to mock/stub a service method or service action ?

My service use the moleculer/elasticsearch mixin. For my unit tests, I want to mock a response for it. Have you a best practice ? Should I used sinonJS or something like that?

Any help would be appreciated.

[johanlelan]

I think I found the solution : jestJS with jest.fn().

[icebob]

Yes, jest.fn() is great for mocking. By the way, check the moleculer tests, how I use Jest for mocking.

[DeadOce4n]

Sorry to revive this issue, but i'm currently struggling to find a way to mock service actions when the action i'm trying to mock is in the same service (eg. this.actions.find), i've already tried something like the following

const broker = new ServiceBroker({ logger: false });
const service = broker.createService(testService);

const findHandler = jest.fn(async () => ['hello']);
jest.spyOn(service.actions, 'find').mockImplementationOnce(findHandler);

[icebob]

Yeah, your solution can work if you call the local action via this.actions.find. If you use ctx.call you should mock the Context as well, or mock the broker.call. The ctx.call calls the broker.call. Example with jest-when: https://replit.com/@icebob/moleculer-jest-mock-demo#index.spec.js

Another example in documentation, how to mock the action handler before createService: https://moleculer.services/docs/0.14/testing.html#Services