@equinor/fusion-observable/src/__tests__/ReactiveObservable.test.ts

WIP

import { Observable, throwError } from 'rxjs';
import { filter, map, tap, withLatestFrom } from 'rxjs/operators';
import { ReactiveObservable } from '../ReactiveObservable';
import type { Epic } from '../types';

type State = { value: string; index: number };
type Action = { type: string; payload: string };
const createTest = (initial: string) => {
  const subject = new ReactiveObservable<State, Action>(
    (state, action) => {
      return { value: action.payload, index: state.index + 1 };
    },
    { value: initial, index: 0 },
  );
  return subject;
};

describe('Reactive observable', () => {
  it('should allow to subscribe', (done) => {
    const expected = ['initial', 'test'];
    const subject = createTest(expected[0]);
    subject.subscribe({
      next: (next) => {
        expect(next.value).toEqual(expected[next.index]);
      },
      complete: () => {
        expect.assertions(expected.length);
        done();
      },
    });
    subject.next({ type: 'test', payload: expected[1] });
    subject.complete();
  });

  it('should allow multiple subscriptions', (done) => {
    const expected = ['initial', 'test'];
    const subject = createTest(expected[0]);
    const assert = (state: State) => expect(state.value).toEqual(expected[state.index]);
    subject.subscribe(assert);
    subject.subscribe(assert);
    subject.subscribe(assert);
    subject.subscribe({
      complete: () => {
        expect.assertions(expected.length * 3);
        done();
      },
    });
    subject.next({ type: 'test', payload: expected[1] });
    subject.complete();
  });

  it('should unsubscribe', (complete) => {
    const expected = ['initial', 'test1', 'test2'];
    const subject = createTest(expected[0]);
    const cache: State[] = [];
    subject.subscribe((x) => cache.push(x));
    expect(cache).toHaveLength(1);
    subject.next({ type: 'test', payload: expected[1] });
    expect(cache).toHaveLength(2);
    subject.unsubscribe();
    try {
      subject.next({ type: 'test', payload: expected[2] });
    } catch (err) {
      expect(err).toBeInstanceOf(Error);
      complete();
    }
  });

  it('should failed to add invalid epic', () => {
    const subject = createTest('test');
    const invalidEpic = () => null;
    try {
      subject.addEpic(invalidEpic as unknown as Epic<Action, State>);
      expect(true).toBeFalsy();
    } catch (err) {
      expect(err).toBeInstanceOf(TypeError);
    }
  });

  it('it should handle epics that fails', () => {
    const subject = createTest('test');
    const epic = () => throwError(() => Error('as expected'));
    const consoleError = console.error;
    console.error = jest.fn();
    subject.addEpic(epic);
    subject.next({ type: 'test', payload: '' });
    expect(console.error).toBeCalledTimes(1);
    console.warn = consoleError;
  });

  it('should reset to initial value', () => {
    const expected = ['initial', 'test'];
    const subject = createTest(expected[0]);
    const initial = subject.value;
    subject.next({ type: 'test', payload: expected[1] });
    expect(subject.value.value).toEqual(expected[1]);
    subject.reset();
    expect(subject.value).toEqual(initial);
  });

  it('should convert to observable', () => {
    const subject = createTest('test');
    const observable = subject.asObservable();
    expect(observable).toBeInstanceOf(Observable);
  });

  it('should handle side effects', (done) => {
    const expectedValues = ['initial', 'dispatched', 'effect'];

    const expectedActions = [
      { type: 'dispatch', payload: expectedValues[1] },
      { type: 'effect', payload: expectedValues[2] },
    ];

    const assertState = (state: State) => expect(state.value).toEqual(expectedValues[state.index]);

    const subject = createTest(expectedValues[0]);
    subject.subscribe({
      next: (state) => {
        assertState(state);
      },
      complete: () => {
        done();
      },
    });

    subject.addEpic((action$, state$) => {
      return action$.pipe(
        filter((x) => x === expectedActions[0]),
        withLatestFrom(state$),
        tap(([action, state]) => {
          expect(action).toEqual(expectedActions[0]);
          assertState(state);
        }),
        map(() => expectedActions[1]),
      );
    });

    const consoleWarn = console.warn;
    console.warn = jest.fn();
    subject.addEffect(expectedActions[0].type, () => {
      throw Error('Should not bork code!');
    });

    subject.addEffect('effect', () => {
      expect(console.warn).toBeCalledTimes(1);
      console.warn = consoleWarn;
      subject.complete();
    });

    subject.next(expectedActions[0]);
  });
});