Я решаю свою проблему, используя:
it('startTimer: should call createSubscribe and set timer with observable emited in 5000ms.', () => {
const scheduler = new TestScheduler((actual, expected) => {
expect(actual).toEqual(expected);
});
scheduler.run(helpers => {
const { expectObservable } = helpers;
const period = 5;
const expected = '5000ms (a|)';
spyOn(helper, <any>'createSubscribe');
helper['startTimer'](period);
expectObservable(helper['timer']).toBe(expected, {a : 0});
expect(helper['createSubscribe']).toHaveBeenCalled();
});
});