how to test effects with filter of ngrx in Angular 4 5 with Jasmine and Marble

Question

I am now facing a problem. not sure how to test if the action$ with filter operator.

I am also trying to follow the rules of https://github.com/vsavkin/testing_ngrx_effects/tree/309b84883c2709a34ab98b696398332d33c2104f

make it simple, I just set the filter if the length of array is 0 return true.

for example:

loadDatas$: Observable<Action> = this.actions$.ofType(LOAD_DATAS_ACTION).pipe(

withLatestFrom(this.store.select(getDatas), (action, datas) =>datas),

filter(data => !data.length),

switchMap(() => {

console.log(‘run api’);

return this.dataApi.find().pipe(

map((datas: Data[]) => new DatasLoadedAction(datas))

………

…..

so I try to write two test cases, one is

expect(effects.loadDatas$).toBeObservable(expected);

when filter return true.

but I don't know how to test if the filter return false.

Do you have any suggestion for this ? thank a lot

Answer 1

You expect the effect to not return a new action, so you can compare it with an 'empty' observable:

const expected = cold('----');
expect(effects.loadDatas$).toBeObservable(expected);