How do you test express controllers that use mongoose models? - unit-testing

Question

In my controller i have a function that creates a user but also checks to make sure that the user does not already exist and then a dashboard function which gets the user from the request and returns any petitions that have been created by that user.
I've looked at mocha, chai and sinon to carry out the tests along with various online resources but have no idea how to begin testing these two functions since they rely on models. Can anyone point me in the right direction to testing the controller or know of any resources which maybe able to help me?
Controller:
const bcrypt = require('bcryptjs');
const passport = require('passport');
const Users = require('../models/Users');
const Petitions = require('../models/Petitions');
const UserController = {
async register(req, res) {
const {name, email, password, passwordCon} = req.body;
let errors = []
// check required fields
if (!name || !email || !password || !passwordCon) {
errors.push({ msg: 'Please enter all fields' });
}
// check passwords match
if (password !== passwordCon) {
errors.push({ msg: 'Passwords do not match' });
}
// check password length
if (password.length < 6) {
errors.push({ msg: 'Password must be at least 6 characters' });
}
// if validation fails, render messages
if (errors.length > 0) {
res.render('user/register', {
errors,
name,
email,
password,
passwordCon
})
} else {
// validation passed
Users.findOne({email: email})
.then(user => {
if (user) {
// user exists
errors.push({msg: 'Email already in use'});
res.render('user/register', {
errors,
name,
email,
password,
passwordCon
});
} else {
const newUser = new Users({
name: name,
email: email,
password: password
});
// hash password
bcrypt.genSalt(10, (error, salt) =>
bcrypt.hash(newUser.password, salt, (error, hash) => {
if (error) throw error;
// set password to hashed
newUser.password = hash;
// save user
newUser.save()
.then(user => {
req.flash('success_msg', 'Registration Success');
res.redirect('/user/login');
})
.catch(error => console.log(error));
}))
}
});
}
},
async dashboard(req, res) {
const user = req.user;
const petitions = await Petitions.find({createdBy: user._id});
console.log('here');
res.render('user/dashboard', {
user: req.user,
petitions: petitions
})
}
};
module.exports = UserController;
Models:
const mongoose = require('mongoose');
const UserSchema = new mongoose.Schema({
createdOn: {
type: Date,
default: Date.now
},
name: {
type: String,
required: true
},
email: {
type: String,
required: true
},
password: {
type: String,
required: true
},
petitions: [
{ type: mongoose.Schema.Types.ObjectId, ref: 'Petitions' }
]
})
const Users = mongoose.model('Users', UserSchema);
module.exports = Users;
const mongoose = require('mongoose');
const PetitionSchema = new mongoose.Schema({
createdOn: {
type: Date,
default: Date.now
},
title: {
type: String,
required: true
},
signaturesNeeded: {
type: String,
required: true
},
description: {
type: String,
required: true
},
createdBy: {
type: mongoose.Schema.Types.ObjectId,
ref: 'Users'
},
signatures: [
{ type: mongoose.Schema.Types.ObjectId, ref: 'Users' }
]
})
const Petitions = mongoose.model('Petitions', PetitionSchema);
module.exports = Petitions;