Cannot connect to MongoDB using Next.js tutorial

Hi all, I’m new to MongoDB and Next.js and am following the MongoDB Next.js integration tutorial working in the project cloned from this example repo.

I am able to get everything in the example repo to work properly, with isConnected to return true from this snippet in /pages/index.js:

export async function getServerSideProps(context) {
  try {
    await clientPromise
    return {
      props: { isConnected: true },
    }
  } catch (e) {
    console.error(e)
    return {
      props: { isConnected: false },
    }
  }
}

`
Then I added an API endpoint at /pages/api/test.js like so:

import { clientPromise } from "../../util/mongodb";

export default async (req, res) => {
  const client = await clientPromise
  const db = client.db('sample_mflix')

  const movies = db
    .collection("movies")
    .find({})
    .sort({ metacritic: -1 })
    .limit(20)
    .toArray();

  res.json(movies);
}

This is the exact same code as provided in the tutorial except that I am importing and using clientPromise instead of connectToDatabase due to updates to the mongodb.js utility file since the tutorial was originally posted. When I try and access the endpoint at localhost:3000/api/test, I get TypeError: Cannot read property 'db' of undefined on the line const db = client.db('sample_mflix').

It seems like clientPromise is returning undefined but I cannot figure out why. Can someone help me understand? Thanks so much.