How to wait for an xhr request in an angular test

I have a component with a button. When the button is clicked, an HTTP request is made:

this.tokensService.create(this.userInCreation).subscribe(nextCb, errorCb);

How do I wait for this request to be completed? Using the async utility and fixture.whenStable does not help me.

For example:

it('', async( async () => {
    fixture.detectChanges();

    appPage.loginButtonEl.click(); // XHR request is initiated here
    fixture.detectChanges();

    await fixture.whenStable();

    // HTTP request is still pending here
}))

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