---

NGXS Testing

$ npm install @ngxs-labs/testing --save-dev

Introduction

@ngxs-labs/testing is package for configures and initializes environment for ngxs unit testing and provides methods for creating states in unit tests.

Simple example

Unit testing is easy with NGXS.

import { NgxsTestBed } from '@ngxs-labs/testing';

describe('Zoo', () => {

  it('it toggles feed', async(() => {
    const { selectSnapshot, dispatch } = NgxsTestBed.configureTestingStates({ states: [ ZooState ] });
  
    dispatch(new FeedAnimals());
    const feed = selectSnapshot(state => state.zoo.feed);
    
    expect(feed).toBe(true);
  }));
  
});

Unit testing actions

Use getStateContextMocks to mock and spy on the first argument of @Actions functions: the StateContext.

With this state:

@State({ name: ZOO_STATE_NAME, defaults: { animals: 1, visitors: 10 } })
class ZooState {
    @Action(ResetAnimalAction)
    public reset(ctx: StateContext<any>) {
        ctx.setState({ animals: 1, visitors: 10 });
        ctx.dispatch(new AddAnimalAction());
    }

    @Action(AddAnimalAction)
    public add(ctx: StateContext<any>, { animalAmount }: AddAnimalAction) {
        const state = ctx.getState();
        ctx.patchState({ animals: state.animals + 1 });
    }
}

getStateContextMocks allows the following tests:

it('should set state and dispatch new action', () => {
    const { dispatch, getStateContextMocks } = NgxsTestBed.configureTestingStates({
        states: [ZooState]
    });
    dispatch(new ResetAnimalAction());

    expect(getStateContextMocks[ZOO_STATE_NAME].setState).toHaveBeenCalledWith({ animals: 1, visitors: 10 });

    expect(getStateContextMocks[ZOO_STATE_NAME].dispatch).toHaveBeenCalledWith(new AddAnimalAction());
    expect(getStateContextMocks[ZOO_STATE_NAME].dispatch).toHaveBeenCalledTimes(1);
});

it('should get state and patch to new value', () => {
    const { dispatch, getStateContextMocks } = NgxsTestBed.configureTestingStates({
        states: [ZooState]
    });
    dispatch(new AddAnimalAction());

    expect(getStateContextMocks[ZOO_STATE_NAME].getState).toHaveBeenCalled();
    expect(getStateContextMocks[ZOO_STATE_NAME].patchState).toHaveBeenCalledWith({ animals: 2 });
});

Mock Select

Use mockSelect to quickly mock selector in component. mockSelect provides a Subject allowing to trigger the mocked selector on demand and with any value.

import { mockSelect } from '@ngxs-labs/testing/jest';

describe('Select tests', () => {
    let foodSelectorSubject: Subject<number>;
  
    beforeEach(() => {
        TestBed.configureTestingModule({
            ...
            imports: [
                ...
                NgxsModule.forRoot([ZooState])
            ]
        }).compileComponents();
    
        foodSelectorSubject = mockSelect(ZooState.feed);

        ...
    });
    
    it('should display mocked value', () => {

        foodSelectorSubject.next(10);
        fixture.detectChanges();
        ...
        expect(food).toEqual(10)
    });
});