I am currently using Firebase Cloud Functions and MongoDB to create my app and here are the files that I have.

module.exports.updateUser = functions.https.onCall(async (data, context) => {
 try {
// Retrieve the relevant data from the arguments
const { username, name, phone, postal, address, gender, dob } = data;
const userID = contect.auth.uid;

// Setting up the database
await connect(process.env.DB_URL);

// Create a schema for the database
const userSchema = new Schema({
  name: String,
  username: String,
  phone: String,
  postal: String,
  address: String,
  gender: String,
  dob: String,
  firebaseUID: String,
});

// Create a new database model
const User = model("users", userSchema);

const user = new User({
  name: name,
  username: username,
  phone: phone,
  postal: postal,
  address: address,
  gender: gender,
  dob: dob,
  firebaseUID: userID,
});

// Saving the user information
await user.save();
return { success: true, response: user };
   } catch (e) {
    return { success: false, error: e };
  }
});

and I would like to test this file. Currently, my test code is as follows:

// Require and initialize firebase-functions-test. Since we are not passing in any parameters, it will
// be initialized in an "offline mode", which means we have to stub out all the methods that interact
// with Firebase services.
const test = require("firebase-functions-test")();

// Chai is a commonly used library for creating unit test suites. It is easily extended with plugins.
const assert = require("chai").assert;

// Sinon is a library used for mocking or verifying function calls in JavaScript.
const sinon = require("sinon");

// Require mongoose so that we can stub out some of its function
const mongoose = require("mongoose");
const { expect } = require("chai");

describe("Test addUser", () => {
  let myFunction, mongooseSaveStub, mongooseConnectStub;

  before(() => {
    mongooseSaveStub = sinon.stub(mongoose, "save");
    mongooseConnectStub = sinon.stub(mongoose, "connect");
    myFunction = require("../index").updateUser;
  });

  after(() => {
    mongooseInitStub.restore();
    test.cleanup();
  });

  it("should pass", async (done) => {
    const updateUser = test.wrap(myFunction);
    const data = { name: "John Higgens" };
    const context = { auth: { uid: "mock" } };
    await updateUser(data, context).then((result) => {
      expect(result.success).toBe(true);
      done();
    });
  });
});

Can I ask 1) how I can test my cloud function, 2) how do I mock or stub the database and 3) where did I do wrongly? The current error that I have is:

Error [ERR_PACKAGE_PATH_NOT_EXPORTED]: Package subpath './lib/encoder' is not defined by "exports"