Observable Test using RxJS

stream-test.js

'use strict';

const assert = require('power-assert');
const {Observable} = require('rxjs/Rx');

describe('Stream', () => {

  const expectedCount = 20;
  // create something stream
  function createStream() {
    return Observable.range(0, expectedCount);
  }

  it('should contain number 10', () => {
    const stream$ = createStream().share();

    const assertCount$ = stream$
      .count()
      .map(count => assert(count === expectedCount));

    const assertContain$ = stream$
      .filter(n => n === 10)
      .count()
      .map(count => assert(count === 1));

    return Observable.merge(
      assertCount$,
      assertContain$
    ).toPromise();
  });
});