I am trying to write unit test for the following function

```
    public loadValues(): Promise<any> {

      return this._http.get(this.url)
         .toPromise()
         .then((values: any) => {
            this.values = values;
         })
     }

```

This function is called by the APP\_INITIALIZER and thats the reason it is returning a promise instead of observable. I did not find any article to test toPromise, any help will be appreciated.

I have the following test written for it

```
it('should return app values', async () => {
    const mockValues = {test: 123};
    spyOn(httpClient, 'get').and.returnValue(of(mockValues)).and.callThrough();
    await service.loadValues();
    expect(service.values).toEqual(mockValues);

    const req = httpMock.expectOne(TEST_URL);
    expect(req.request.method).toBe('GET');
});

```