大理石测试可观察到方法调用后发生了变化? [英] Marble testing observable that changes after a method call?

问题描述

在Angular 8中，我有一个具有只读Observable属性的服务，该属性是从BehaviorSubject<string>派生的，该属性包含描述服务状态的字符串.服务中还包含更改服务状态的方法.

export class StateService {
  private _state = new BehaviorSubject<string>('before');

  readonly state$ = this._state.asObservable();

  constructor () { }

  begin() { this._state.next('during'); }

  finish() { this._state.next('after'); }

  reset() { this._state.next('before'); }
}

我想做的是在Jasmine套件中编写大理石测试，以优雅地测试此可观察值的价值，因为它会发生变化.

let scheduler: TestScheduler;

beforeEach(() => {
  scheduler = new TestScheduler((actual, expected) => {
    expect(actual).toEqual(expected);
  });
});

it('should flow states correctly', () => {
  scheduler.run(({expectObservable, flush}) => {
    const svc = setupSvc(); //Call to a function in the suite that sets up the StateService

    svc.begin();
    svc.finish();
    svc.reset();

    flush();

    expectObservable(svc.state$).toBe('a-b-c-d', {
      a: 'before',
      b: 'during',
      c: 'after',
      d: 'before'
    });
  });
});

我尝试了调用begin，finish，reset和调度程序的flush助手的各种组合，但是期望总是只报告一个初始值(a大理石)，而没有其他人.

要实现这一目标，我缺少什么?还是大理石是测试该方法的错误方法?

解决方案

订阅通过测试帮助程序生成的冷可观察结果似乎可行:

it('should flow states correctly', () => {
  scheduler.run(({ expectObservable, cold }) => {
    const svc = new StateService();

    cold('--a-b-c', {
      a: 'begin',
      b: 'finish',
      c: 'reset'        
    }).subscribe(methodName => {
      svc[methodName]();
    })

    expectObservable(svc.state$).toBe('a-b-c-d', {
      a: 'before',
      b: 'during',
      c: 'after',
      d: 'before'
    });
  });
});

Stackblitz

In Angular 8, I have a service with a readonly Observable property, spawned from a BehaviorSubject<string> that contains a string describing the service's state. Also in the service are methods that change the state of the service.

export class StateService {
  private _state = new BehaviorSubject<string>('before');

  readonly state$ = this._state.asObservable();

  constructor () { }

  begin() { this._state.next('during'); }

  finish() { this._state.next('after'); }

  reset() { this._state.next('before'); }
}

What I want to do is write marble tests in my Jasmine suite to elegantly test the value of this observable as it would change.

let scheduler: TestScheduler;

beforeEach(() => {
  scheduler = new TestScheduler((actual, expected) => {
    expect(actual).toEqual(expected);
  });
});

it('should flow states correctly', () => {
  scheduler.run(({expectObservable, flush}) => {
    const svc = setupSvc(); //Call to a function in the suite that sets up the StateService

    svc.begin();
    svc.finish();
    svc.reset();

    flush();

    expectObservable(svc.state$).toBe('a-b-c-d', {
      a: 'before',
      b: 'during',
      c: 'after',
      d: 'before'
    });
  });
});

I've tried varying combinations of calling begin, finish, reset, and the scheduler's flush helper, but the expectation always reports just the one initial value (the a marble) and no others.

What am I missing to be able to pull this off? Or are marbles the wrong way to go about testing this?

解决方案

Subscribing to a cold observable produced via the test helper seems to work:

it('should flow states correctly', () => {
  scheduler.run(({ expectObservable, cold }) => {
    const svc = new StateService();

    cold('--a-b-c', {
      a: 'begin',
      b: 'finish',
      c: 'reset'        
    }).subscribe(methodName => {
      svc[methodName]();
    })

    expectObservable(svc.state$).toBe('a-b-c-d', {
      a: 'before',
      b: 'during',
      c: 'after',
      d: 'before'
    });
  });
});

Stackblitz

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