Setting up a unit testing environment in Node.js


Example Project


In this post we'll go through the complete process of setting up your test environment in a Node.js app, and then write a few simple unit tests. Although I've aimed this for Node apps, you should be able to follow these steps for any JavaScript setup such as Ionic.

Before reading reading this article you should already know:

1. Setting up a Testing Framework

A testing framework will take care of the overall test structure for us and make it easy to run our tests and allow us to use additional plugins too if necissary (such as generating HTML test reports, or providing coverage test features). It is possible to do all this with vanilla JavaScript, but a lot more work

The two most popular test frameworks are Mocha and Jasmine. For this we will be using Mocha.

Since we will use the 'mocha' command, we must first install Mocha globally. If not you will get the error message 'mocha is not recognized as an internal or external command' (or mac equivalent).
npm install mocha --global

If your using git, or have multiple developers working on the project you'll also want to add mocha to your package.json so others can just run npm install to populate their node_modules.
First initialize your package.json (if you haven't already done so):
npm init

Then add mocha to your devDepenencies and save in node_modules by running
npm install mocha --save-dev

Next we need to create a directory to store our tests. By default mocha will look for a folder called 'test' inside the projects root, so we must use this name exactly.
mkdir test


The following commands can be used to setup mocha in a new project. (mac commands might be slightly different)
mkdir test-example && cd test-example :: create new projet director

npm i mocha -g :: install mocha globally so the mocha command can be used

npm init :: initialise package.json

npm i mocha -D ::  add mocha to your projects devDependancies

mkdir test :: create new folder for tests

2. Setting up an Assertion Library

Node does have some assertion test functionality built in, although it is quite basic, and not particularly nice to use. So instead we are going to use Chai as an assertion library - there several others out there, but chai is good and well established with good documentation.
So first off we need to install chai to our project like we do with all node modules:
npm install chai --save-dev

Next we are going to create a file to put our test in. Remember this should be inside the test directory. The file can be called what ever you like (but keep it relevant), and the extension should be .js (or .coffee if your writing your tests in CoffeeScript).

Inside your new test file, the first step is, as usually done with node modules, to include the module in your file.
var chai = require('chai');

If you visit the Chai website( you will see that chai has three interfaces: Should, Expect and Assert.

It is up to you which one you use, and it's easily possible to use a combination. They all work in a similar way, with the only main difference being the syntax and the structure of the test blocks you write. Should is much more like English, and Assert is more like conventional JUnit comparisons, Expect is somewhere in between.

So if we were using expect, the fist thing we would need to do is define the expect method.
var expect = chai.expect;

The format of your tests will have a describe block for what the code module should have been tested for, followed by a series of it's containing the Chai tests, in this format:
describe('JavaScript example test', function(){
    it('should return true in JavaScript',function(){

The format of an expect method is like this:

Example from the Chai documentation, view more here:

3. Running Tests, and specifying additional options

Once you have a sample test, like above. You can run it to see the result.
To run all tests in the command line, use the following command:

Running tests from a single file

If you'd like to run just tests from a single file, you can type mocha followed by the path to the test file.

Specifying test path in package.json

It's good practice to specify a command to execute your tests in your package.json. 
This will allow other developers to run 'npm test' on any project whatever testing framework or setup is implemented.
In the scripts section, where you've specified the entry point, add a test command:
"scripts": {
    "start": "node ./bin/www",
    "test": "mocha",

This will mean you can run npm test and npm will run the mocha command.

Passing additional parameters to mocha

With mocha, it's possible to pass it additional parameters to specify options such as how tests are run. 
You can change things like, how results are displayed, what language you write your tests in (e.g coffee), whether it should look in sub-directories or not, the timeout etc......
This can be done with the ordinary flag syntax, e.g.
mocha --reporter nyan --recursive

You can see a full list of flags here:

The above command will set the reporter (how results are displayed) to be Nyan cat (check it out, it's pretty cool), and the recursive flag will mean that mocha will also execute tests in sub-directories.

But, it's a bit of a pain having to specify all those flags instead of just calling the mocha command. So you can instead create a file called 'mocha.opts' inside your test directory. In this file you can specify a list of flags. Then you can just run the mocha command, without typing any parameters in the command line.

Put each flag on a new line, and use long flags rather than short-hand so that it's clear for other developers. Here is an example mocha.opts file:

4. Coverage Testing

See coverage testing confluence article here: 


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Introduction to Test Driven Development

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First off, what do tests provide us with?

  • Documentation code
  • Catch future errors
  • Long-term time savings - because errors have been found before anythings been deployed to production
Although all the above are true, using tests like this is just a tool - not a process.

What is TDD?

In it's simplest form TDD comes down to the following process:
  • Decide what the code will do
  • Write a test that will pass if the code does that thing
  • Run the test, to prove it will fail
  • Write the code
  • Run the test again, to see it pass
It's important to note that you must not write the code, until you've written the test.
Also it is essential to ensure the test actually fails first, it is surprisingly easy to make a small mistake in your test case that means your test will always pass, and that's not the type of error that anyone likely to look into. It's also sometimes necessary to back-test, where you break the code to show that the test fails.
This should be done for every couple of lines of code, every method.

What does TDD provide?

  • Design and plan before you code
  • Documenting your design before you build it
  • Proving that the code implements that design
  • Encouraging the design of testable code - very important!!
Testable code, is good code!
This is because if you have long methods/ functions with loads of if statements and stuff, it's just not possible to write tests. If you write the tests first, you can't write the code that is too complicated.

Testable code is:

  • Modular, as we're forced to break things down so we can test them
  • Decoupled design, if our objects or methods are too tightly interwoven, we can't test them independantly.
  • Methods should have limited scope, and not trying to do too much in one place
  • etc... 
Basically good testable code will have a much lower cyclomatic complexity. This is the measure of how many different paths there are through the code, so essentially every conditional statement you add, will give you another route and another set of tests.

If your finding the test complicated to write, then that's a code smell, your going about it the wrong way.

Result of TDD

Better code in less time *

*so it might not feel like it's going faster, because it's a process rather than just hacking. And processes feel tedious. Also it may take some practice to get up to speed, but it's fully worth it in the long run for speed and code quality.

Use your judgement about when to test

Although nearly all code should be tested thoroughly there are some exceptions:
  • Some things are too hard to test - especially where external services are involved
  • Some tests are too trivial to be useful
  • Over-testing is possible 
  • Exploritory codeing, whern your not sure how it's going to be used. SO not for production code.

Links for learning more about TDD

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How to write a gulpfile

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Setting up a new project and getting it ready for Gulp

Gulp is simple to set up. Presuming you have Node.js already installed:
  • In the command line, navigate into the root of your project working directory
  • Install Gulp with npm install gulp --save-dev what this will do will add gulp into your node_modules folder. The --save-dev part will add gulp to your devDependacies in your package.json file. It is similar to --save/-s only it's a dependency that's only required for development of your app.
  • Create a new JavaScript file in your project root directory called gulpfile.js 
  • This is the file where we will put all our build configuration in...

How to write the gulpfile.js

Install Plugins

Firstly you'll need to install and include the plugins you need. Every task in Gulp uses a plugin. For this example we'll be compiling sass. 
If you haven't already done so, in your console run:
npm install gulp --save-dev

npm install gulp-sass --save-dev

This will install both gulp and our first plugin in, gulp-sass. It will also add the dev dependency to our package.json

Require Necessary Modules

Back to the gulpfile.js in the same way that you'd use any other node module we need to include it. So in the top of your gulpfile.js paste the following code:
var gulp = require('gulp');

var sass = require('gulp-sass');

Creating a gulp task

Now we need to actually write the code to tell gulp what to do with this plugin.
To do this we call the task method in gulp. This method takes to parameters, firstly a string which can be what ever you want to call your task (in this example I called is sass - seems to make sense). 
Secondly we pass it a function that does the work. The format of this function is:
  • First pass is a glob of which files and folders to look for, this is done with the gulp.src method (in this example it's all files withing the scss folder with the file extension .scss).
  • Then we call gulp's pipe method on that file selection, where we pass it the plugin as a parameter.
  • Then finally we give gulp a destination location where the processed files should be saved. We do this using the gulp.dest method.  

gulp.task('sass', function() {
    return gulp.src('scss/*.scss')

Running the Gulp task

Try testing out what we wrote above by running the following command in the console
gulp sass
This will look for the gulpfile.js in current directory, then look for the task called 'sass' and run it.
What you should see is all your sass code inside the sccss directory is compiled to css and aved in your css directory.

Watching files for changes

Now what would be really good is if gulp could just wait until everytime we make a change to our sass and then compile it into CSS automatically. This is actually really easy to set up using gulp watch.
gulp.task('watch', function() {'scss/*.scss', ['sass']);

We have named this task 'watch', and what it is doing is watching for changes in .scss files inside the scss folder and then running the 'sass' task.
If you also had a coffeescript task, you could just add another line inside this method looking something like this:'cscripts/*.coffee', ['coffee']);

Including Multiple Plugins in a single task

It's strait-forward to run multiple operations at once. For example process all your scripts in one task, or process all your images in another. e.g.
gulp.task('scripts', function() {
    return gulp.src('js/*.js')

Default Task

If we name a gulp task 'default' it becomes the default task and you can run it by simply running
(instead of gulp task-name)

We can set our default task to run several tasks for us. For example:
gulp.task('default', ['sass', 'lint', 'coffee', 'watch']);

(presuming you already have a 'sass', 'lint', 'coffee' and 'watch' task) it will run all the listed task.

Prerequisite Tasks

In a similar way, you can set prerequisite tasks to run, by listing them after the task name.
gulp.task('coffee', ['coffee-lint'], function(){
return gulp.src('cs/*.coffee')

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Introduction to automating your tasks with the gulp.js build tool

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What is Gulp?

Gulp.js is a streaming build system built on Node.js. This basically means that it can be configured to perform repetitive tasks and coding operations automatically during development. For example it can compile all your coffee scr
ipt whenever your file changes, or it can minify your CSS, or maybe synchronize all your development browsers and constantly refresh them on file change. 

Gulp uses a variety of plugins to do these tasks, and there is a plugin to do pretty much everything you'd need to do very easily. If you can't find one to do a particular operation, you can make your own ;)

Why do I need to use a build system?

For all modern web applications (hybrid apps, sites, web backends...) there are certain tasks that are almost essential to ensure high quality. For example checking your JavaScript for errors, minifying it, concatenating it. There are also certain tasks that just make developing easier, like having your your app tested in every browser and screen size whenever your file changes or monitoring file sizes and network requests.

It is true that it is possible to do most of these tasks without a build system or tool in place, but using something like Gulp or Grunt is much more efficient, easy to use, fast and keeps development code to a minimum and all in one place. 

Example Gulpfile for a typical Node.js Express app

I've created a Gulpfile for a typical Node Express project that uses coffee script and Less. It is just intended as a working example of how you can integrate everything together, so you can modify it to meet your specific project needs.

Setting up example project

  1. Open the console and navigate into a new working directory
  2. Run the command: git clone
  3. Install the dependencies by running: npm install
  4. Start the gulp script bu running: gulp
So what the above steps should have done is: download the example project from GitHub, install all it's dependenceies found in the package.json and put them in the node_modules folder. Running gulp will then call the default task inside the gulpfile.js

What this project does

If you look in the gulpfile.js you'll see there's a whole load of tasks that are being covered. Mainly around processing the CSS and JavaScript ready for production. You can view the full list of tasks in the for the Git repo.

Testing it out

So once you've run the above commands in the terminal, if everything worked as it should have done your web browser should have opened. If it didn't try visiting http://localhost:4000. (If there is nothing, then check the console for errors.)

Browser Sync

If you open another browser and view the same URL you'll notice that the two browsers are in sync. So if you scroll down on one, the other will scroll, if you click a link on one all browsers will follow. This is really really useful testing your app out on a range of browsers and screen sizes all at once without having to even do any clicking, works better if you have a decent number of monitors ;) 
It's done using a gulp plugin called browser-sync.


Secondly you'll notice if you make any changes to any of the jade templates or views it will update live, across all your browsers as you code. No refreshing needed :) (you do need to set your IDE to autosave on keyup though, which should be default if your using any half decent ide). This is done using nodemon in gulp.

Linting, Compiling, Concatinating, Piping.... styles and scripts

Now for the coolest part, in your working directory open up the sources folder. If you edit any of the CSS, Less, JavaScript, CoffeeScript files you'll see that as it saves it creates a new version of the production code in your public directory, and refreshes the browsers accordingly. The code in the public directory is all minified and had everything else done to it to make it awesome and really efficient. Check the console for a list of all the tasks gulp has just done.


  1. Try creating and modifying the JavaScript and CoffeeScript files in the javascript source directory, then look in the public directry and see what they're looking like in production form.
  2. In a similar way modify the CSS and Less file, you should see the changes in the browser
  3. Have a read through gulpfile.js and modify the configuration to suit your project, then test it out.
  4. Install a new gulp-plugin and set it up by seeing how the rest have been done
  5. Try running some of the tasks individually, for example gulp clean should just clean the public directory and gulp-watch should just watch for changes and update files accordingly.
If the console freezes, cancel the process (Ctrl+C) and rerun gulp.

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