Abstracting class using mongoose - node.js

Question

I'm developing an application in which I need to have some abstraction.
I mean there, that I would like to "simulate" an interface behaviour like creating a contract inside of my concrete classes.
Actually, dealing with Users, I'm having a UserMongoRepository class with the contract implemented :
getAll() returns the full list of users by promise
getById(id) returns the user concerned by promise
save(user) saves the user by promise
... etc
I have the same methods implemented inside of the UserMysqlRepository (allowing me to switch behaviour when a change is needed.
Problem
My problem is that I'm dealing with Mongoose that doesn't act like a datamapper, but more like an active record.
It means that my implementation of save(user) would be a bit weird like following :
save(user){
let mongooseUser = this.convert(user);
return user.save();
}
The convert method allows me to switch from a standard Model to a specific Mongoose model. It allows me, again, to have some abstraction and to don't have to rewrite my full application data access.
My real problem is when I try to unit test my full class :
import MongooseUser from '../../auth/mongooseModel/MongooseUser';
/**
* UserMongoRepositoryclass
*/
export default class UserMongoRepository{
/**
* Create an UserMongoRepository
*/
constructor(){
}
/**
* Convert a User to a MongooseUser
*/
convert(user){
return new MongooseUser({email:user.mail,password:user.password,firstname:user.firstName, lastname:user.lastName});
}
findById(id){
return MongooseUser.find({id:id});
}
save(user){
return user.save();
}
}
In a standard way, I would inject my DAO inside of my constructor, and being able to mock it.
In the case of mongoose, it's a bit disturbing, because the element that makes the job isn't an instantiated object (so that I can mock it) but a class definition imported at the top of the document.
Solutions
Should I pass the MongooseUser class definition as a parameter inside of the constructor ?
Implying that I will have this code inside of the convert method :
let user = new this.MongooseUser({})
Have you got a better idea, to abstract mongoose behaviour in data mapper way ?
I don't want to use another module, it's, in my sense, the most advanced one with NodeJS...

Answer 1

I'm not familiar with the import syntax (nor EMCASCRIPT-6), though you say you're using node.js, so I'd recommend using the proxquire package. The idea is that the package allows you to require an external package, while stubbing the requirements that that package would use. So in your case, you could do something like:
proxyquire('../my/class/that/uses/mongoose', {
mongoose: MyTestMongooseImplementation
})
Which would allow you to use your own mongoose implementation while still using your MongooseUser as you have defined it in your package. Alternatively, you could just override the the MongooseUser class (path relative to the the file whose requirements you are stubbing:
proxyquire('/path/to/UserMongooseRepository', {
'../../auth/mongooseModel/MongooseUser': MyTestMongooseUser
})
Documentation: https://www.npmjs.com/package/proxyquire