Mongo Schemas - Mongoose error when Mocha Testing (MissingSchemaError and OverwriteModelError)

Question

Edit - It seems I had two issues here. I have accepted the answer given below but please read the comments because the mocha -w issue was just as significant in the fix.

I've read a few SO questions and answers on this and tried a few of the suggested methods but I'm still not able to resolve this issue so I'm hoping someone can help me:

I have a model:

const mongoose = require('mongoose');
mongoose.Promise = global.Promise;
const slug = require('slugs');

const storySchema = new mongoose.Schema({
  name :{
    type: String,
    trim: true,
    required: 'Please enter a store name'
},
  slug: String,
  storyText: {
    type: String,
    trim:true
},
  keyStageLevel: [String]
});


module.exports = mongoose.model('Story', storySchema);

and a storyController:

const mongoose = require('mongoose');
const Story = mongoose.model('Story');

exports.storyHomePage = (req, res) => {
console.log(req.name);
res.render('story', {
    title:"Reading Project = Story Home Page",
    created:req.query.created

  });
};

and I have mocha running some tests. However when I run the test I get an error

MissingSchemaError: Schema hasn't been registered for model "Store".

Reading this https://stackoverflow.com/a/21915511/1699434 I can modify my storyController to

const mongoose = require('mongoose');

mongoose.model('Story', new mongoose.Schema());

const Story = mongoose.model('Story')

which keeps Mocha happy but then nodemon blows up with an error

OverwriteModelError: Cannot overwriteStorymodel once compiled.

Looking around this https://stackoverflow.com/a/19051909/1699434 seems like the go to answer for this issue but as far as I can see I'm using that approach (I use const Store = mongoose.model('Store'); instead of const Store = require('../models/Store'))

So I'm a bit stuck. Any help much appreciated!

Edit to include start.js

const mongoose = require('mongoose');


// import environmental variables from our variables.env file
require('dotenv').config({ path: 'variables.env' });

// Connect to our Database and handle any bad connections
mongoose.connect(process.env.DATABASE);
mongoose.Promise = global.Promise; // Tell Mongoose to use ES6 promises
mongoose.connection.on('error', (err) => {
  console.error(`${err.message}`);
});

//import all of the models
require('./models/Story');

// Start app
const app = require('./app');
app.set('port', process.env.PORT || 7777);
const server = app.listen(app.get('port'), () => {
console.log(`Express running → PORT ${server.address().port}`);
});

Answer 1

You should import the Story model using the following syntax, And there is no need to import mongoose module again:

// I suppose the file is located in 'models' folder and the current folder is 'controllers'
const Story = require('../models/story');

By doing const Story = mongoose.model('Story'); you are creating a Story model without a schema definition and that's why you get Schema hasn't been registered for model "Store".

In you second example:

// this create a new model from an empty schema (schema without fields)
mongoose.model('Story', new mongoose.Schema());

// overwriting the first model which is not allowed by mongoose
const Story = mongoose.model('Story')

Remember that mongoose.model() method only defines model from schema that maps to a MongoDB collection