How to get return the id in buffer form in nodejs

Question

I have a test db with only 1 record and I've checked that the record is in the DB using the following code:

const prod = await Product.findOne({_id: params.ProductID}).exec();
console.log(prod) 

My codebase has a lot of these types of queries. I cannot rewrite every query in the db so I need to make my testing work with the code that is already in place.

Product.findByIdAndUpdate(new Buffer(params.productID, 'base64').toString('hex') 

I am having difficulty testing this because I am getting record not found. I feel like the record id has already been converted before I pass it in and the query is manipulating it which is why I can't find the record.

How can I send the id that this query is looking for?