Mock OAuth2Client for testing (google-auth-library)

mock-snippet.ts

import { LoginTicket, OAuth2Client, TokenPayload } from "google-auth-library";

const mockTokenPayload: TokenPayload = {
 //... 
}

const mockVerifyIdToken = ({
  idToken,
}: {
  idToken: string;
}): Promise<LoginTicket> => {
  return new Promise((resolve, reject) => {
    if (idToken === "invalid") {
      reject(new Error());
    }
    resolve({
      getPayload: (): TokenPayload => mockTokenPayload,
    } as LoginTicket);
  });
};

OAuth2Client.prototype.verifyIdToken = mockVerifyIdToken;