Karma/Jasmin Test Promise error inside of regular function - promise

Question

First my Setup. I try to test some of my Ionic Pages etc.
And I have a login page where I want to test the Login.
This is my Login method:
doLogin() {
let authHelper = this.injector.get(AuthHelper);
authHelper.sendSignInLink(this.email).then(()=> {
window.localStorage.setItem("userMail", this.email);
let loginToast = this.toast.create({
message: "Link to email succesfully send. In order to finish the login, it is necessary to click the send link.",
duration: 3000,
position: "bottom",
});
loginToast.present();
}).catch(() => {
throw new EmailSignInLinkError("invalid Mail");
});
}
As we can see the method sendSignInLink is returning a promise and if the promise is rejected it should throw a custom error.
For my unit test I mocked the authHelperClass to a very simple mock:
export class AuthHelperMock {
public auth(): Promise<any> {
return new Promise((resolve, reject) => {
resolve(2);
});
}
public sendSignInLink(email: String): Promise<any> {
return new Promise((resolve, reject) => {
if (email != undefined || email != "")
resolve(1);
else
reject("Invalid email");
});
}
}
Now is the Problem that I try to check on this thrown error from my promise.
My it case is:
it('should not do the login', () => {
component.email = "";
expect(() => {
component.doLogin();
}).toThrowError(EmailSignInLinkError)
I know that this will not work because the promise is async and the case will fail before it throws the error. But I don't find any suitable solution beside changing my doLogin to a promise as well.
How can I check on this Promise within a regular function?