Testing private rxMethods in SignalStore

[MotassemJa]

I have a signalStore that has a private method to fetch some data and I call it in the onInit Hook of the store:

withMethods(store => ({
  _fetchData: rxMethod<void>(pipe(
    switchMap(() => inject(Service).getData().pipe(
      ...
    ))
  ))
})),
withHooks({
  onInit(store) {
    store._fetchData()
  }
})

How can I unit test the private method with jest?

[twittwer]

Do you want to test the internals or the behaviour of the store?

For the store behaviour, you may spy on the service method, instantiate the store and check for the service call.

[MotassemJa]

I want to test the logic when the _fetchData is called. Like when an error is thrown by the service for example, the error state should be updated.

[rainerhahnekamp]

Every private method has an impact on the outside/public. In your case, you want to test that the error state is updated.

Provide a test double for Service, let it throw an error, and verify that the state got the expected change.

[MotassemJa]

Okay sounds fair. But for some reason it seems that the onInit Hook is not being called when configuring the test with TestBed:

const getDataMock = jest.fn().mockImplementation(() => of([dataStub()]));
beforeEach(() => {
  TestBed.configureTestingModule({
    providers: [
      MySignalStore, 
      { provide: Service, useValue: { getData: getDataMock }}
    ]
  });
  store = TestBed.inject(MySignalStore);
});

it('should call getData', () => {
  expect(getDataMock).toHaveBeenCalled() // fails
})

[MotassemJa]

I had a typo in my providers array which caused the error, sorry for that.