Rationale

This library aims to provide helpers to test Angular apps that are not provided natively. For now it especially focusses on timing issues with rx.

Features

Whats wrong with Angulars test helpers

Suppose you want to test following code:

function delayOneSec(val) {
    return Observable.of(val).delay(1000);
}

To test this in Angular, you could write:

describe('my suite', () => {
    it('should wait one second', fakeAsync(() => {
        let result = null;
        delayOneSec('hello').subscribe(v => result = v);
        expect(result).toBeNull();
        tick(1000); // Move time forward 1 second
        expect(result).toBe('hello');
    });
});

This test would fail. That is because the rx delay() operator doesn't only use setTimeout() or setInterval() internally, but also uses the rx Scheduler now() method to check whether time has really passed. By default it uses Scheduler.async of which the now() function resolves to getting the current time. See angular issue #8678

Solution provided by this lib

When this library is used, the Scheduler.async.now() function is overridden to return a virtual time. This time is automatically put forward when the tick() function of this library is called.

In addition it provides setFakeTime() to set the time manually.

Usage

Instead of importing tick() from '@angular/core/testing', import it from this library. So instead of

import { fakeAsync, tick } from '@angular/core/testing';

use

import { fakeAsync } from '@angular/core/testing';
import { tick } from 'angular-testing-ext';

Conclusion

Lets hope Angular will provide it's own way of dealing with this in the future.