Testing node.js with mocha and chai

Question

I've been successfully testing my API endpoint built with node.js but still can't figure out how to test this kind of "non async" code.

/**
 * Database service
 */
// Dependencies
const fs = require('fs');
const path = require('path');
const Sequelize = require('sequelize');
const basename = path.basename(module.filename);
let db = {};

// Connection
let sequelize = new Sequelize(process.env.DATABASE_URL, {logging: false});

// Models processing
fs
    .readdirSync(__dirname)
    .filter(file =>
        (file.indexOf('.') !== 0) &&
        (file !== basename) &&
        (file.slice(-3) === '.js'))
    .forEach(file => {
        /* uncovered */ const model = sequelize.import(path.join(__dirname, file));
        /* uncovered */ db[model.name] = model;
    });

Object.keys(db).forEach(modelName => {
    /* uncovered */ if (db[modelName].associate) {
    /* uncovered */     db[modelName].associate(db);
    /* uncovered */ }
});

db.sequelize = sequelize;
db.Sequelize = Sequelize;

// Export everything
module.exports = db;

This is just a simple part of code which load all my Sequelize models (.js files) and create the associations.

While testing with istanbul, mocha and chai I can get full coverage over my API functions but can't get this code covered.

How should I test this?

Answer 1

If you want to test something using the fs, IMHO you should use dependency injection in your module. This will aloow you to mock the fs:

 /** * Database service */ // Dependencies const Sequelize = require('sequelize'); makeDb = (fs, path) => { let db = {} const basename = path.basename(module.filename); // Connection let sequelize = new Sequelize(process.env.DATABASE_URL, { logging: false }); // Models processing fs .readdirSync(__dirname) .filter(file => (file.indexOf('.') !== 0) && (file !== basename) && (file.slice(-3) === '.js')) .forEach(file => { /* uncovered */ const model = sequelize.import(path.join(__dirname, file)); /* uncovered */ db[model.name] = model; }); Object.keys(db).forEach(modelName => { /* uncovered */ if (db[modelName].associate) { /* uncovered */ db[modelName].associate(db); /* uncovered */ } }); db.sequelize = sequelize; db.Sequelize = Sequelize; return db } // Export everything module.exports = makeDb; 

Then you use your module like this:

 //app.js const fs = require('fs') const makeDb = require("./db") const db = makeDb(fs, path) /* * DO SOME STUFF */ //db.test.js const fakeFs = require('mock-fs') const makeDb = require("./db") const testDb = makeDb(fakeFs, path) 

This allows you to pass a fake FS to do your tests with mocka.

Mock-fs : https://www.npmjs.com/package/mock-fs