How to properly unit test a nodeJS + mongoose app with Jest

I am having some serious trouble wrapping my head around how to unit test the mongoose ORM piece of my app. I am starting to think using mongoose isn't worth all the effort..

Edit: forgot to mention - I am using Jest as the test framework.

So what I have is simple entity called Detail. Below is the code setup.

detail.model.js

const mongoose = require("mongoose");

const { Schema } = mongoose;

const schema = new Schema({
  refId: Number,
  text: String,
  dateCreated: { type: Date, default: Date.now },
  createdBy: { type: mongoose.Schema.Types.ObjectId, ref: "User" }
});

module.exports = mongoose.model("Detail", schema);

detail.service.js

const db = require("../../_helpers/db");

const { Detail } = db;

async function getAll({ createdBy }) {
  return Detail.find({ createdBy });
}

async function create(payload) {
  return new Detail(payload).save();
}


module.exports = {
  getAll,
  create
};

and the helper db.js

db.js

const mongoose = require("mongoose");
const User = require("../users/user.model");
const Detail = require("../entities/detail/detail.model");
const logger = require("../logging/winstonLogger");

mongoose.connect(process.env.MONGODB_URI, {}, err => {
  if (err) return logger.error("Failed to connect to DB", err);
  logger.info("DB connection established!");
});

module.exports = {
  User,
  Detail
};

So the setup is pretty basic. And it works, to a degree. I've tested it with postman (there's some more code involved to support express routing).

What I am trying to do is unit test the entity service but it just wont work. The Detail model resolves and the constructor fails/

const mongoose = require("mongoose");

jest.mock("mongoose");

jest.spyOn(mongoose, "connect").mockImplementationOnce(() => {
  console.log("Mock connect triggerred!");
});

const mockUser = {
  username: "admin",
  firstName: "Rick",
  lastName: "Sanchez"
};

describe("Detail Service", function() {
  describe("Given a valid detail", function() {
    it("should create a new detail", async function(done) {
      const detailService = require("../../src/entities/detail/detail.service");

      const detail = {
        refId: "507f1f77bcf86cd799439011",
        text: "This is a test detail 1",
        dateCreated: Date.now(),
        createdBy: mockUser
      };

      const mongooseResult = await detailService.create(detail);
      done();
    });
  });
});

Detail is not a constructor
TypeError: Detail is not a constructor
    at Object.create (C:\x\x\x-server\src\entities\detail\detail.service.js:14:10)