index.js

/// <reference types="cypress" />
// ***********************************************************
// This example plugins/index.js can be used to load plugins
//
// You can change the location of this file or turn off loading
// the plugins file with the 'pluginsFile' configuration option.
//
// You can read more here:
// https://on.cypress.io/plugins-guide
// ***********************************************************

// This function is called when a project is opened or re-opened (e.g. due to
// the project's config changing)
const { promisify } = require("util");
const { google } = require("googleapis");
const { OAuth2Client } = require("google-auth-library");
const fs = require("fs");
const pify = require("pify");
var unescape = require("lodash.unescape");
const gmail = google.gmail("v1");
const gmailGetMessagesAsync = promisify(gmail.users.messages.get);
const gmailListMessagesAsync = promisify(gmail.users.messages.list);
// Promisify with promise
const readFileAsync = promisify(fs.readFile);
// Gmail label list
const gmailListLabesAsync = promisify(gmail.users.labels.list);
const TOKEN_DIR = __dirname;
const TOKEN_PATH = TOKEN_DIR + "/gmail-nodejs-quickstart.json";
/**
 * @type {Cypress.PluginConfig}
 */
module.exports = (on, config) => {
  // `on` is used to hook into various events Cypress emits
  // `config` is the resolved Cypress config
  on("task", {
    "gmail:get-messages": async () => {
      // Get credential information
      let confirm_msg;
      const content = await readFileAsync(__dirname + "/client_secret.json");
      // specify the client secret file
      const credentials = JSON.parse(content);
      // credential
      // authentication
      const clientSecret = credentials.installed.client_secret;
      const clientId = credentials.installed.client_id;
      const redirectUrl = credentials.installed.redirect_uris[0];
      const oauth2Client = new OAuth2Client(
        clientId,
        clientSecret,
        redirectUrl
      );
      const token = await readFileAsync(TOKEN_PATH);
      oauth2Client.credentials = JSON.parse(token);

      let res = await gmailListMessagesAsync({
        auth: oauth2Client,
        userId: "me",
        maxResults: 1,
      });

      const newestMessageId = res["data"]["messages"][0]["id"];

      res = await gmailGetMessagesAsync({
        auth: oauth2Client,
        userId: "me",
        id: newestMessageId,
      });

      let body_content = JSON.stringify(res.data.payload.body.data);

      let data, buff, text;
      try {
        data = body_content;
        buff = new Buffer.from(data, "base64");
        text = buff.toString();

        let regex = /https?:\/\/[\-A-Za-z0-9+&@#\/%?=~_|$!:,.;]*/g;
        let filtered = text.match(regex);
        filtered = filtered.filter(
          (item) => !item.includes("www") && item.length > 500
        );
        filtered = Array.from(filtered);
        filtered = filtered.shift();

        confirm_msg= unescape(filtered);
      } catch (err) {
        console.log("error");

        data = body_content;
        buff = new Buffer.from(data, "base64");
        text = buff.toString();

        let regex = /https?:\/\/[\-A-Za-z0-9+&@#\/%?=~_|$!:,.;]*/g;
        let filtered = text.match(regex);
        filtered = filtered.filter(
          (item) => !item.includes("www") && item.length > 500
        );
        filtered = Array.from(filtered);
        filtered = filtered.shift();
        confirm_msg = unescape(filtered);
      }
      
      return confirm_msg;
    },
  });
};

Read gmail api with cypress