Automatic REST JSON API test using Node.js + Mocha + Chai

This text was originally posted in Brazilian Portuguese here.

REST API is present in the majority of the projects that we work nowadays, and achieve a good sleeping night knowing that all endpoints are ok is part of the job. To reach this goal, automation is crucial.

In this article I will list the steps I made to create my first automated test using Node.js, the test framework Mocha and Chai, the lib that help us to write the test cases.

Installation

All the steps bellow were executed using a PC running Windows 10 and MinGW, but since these tools are cross platform, it shouldn't be so different in other systems.

First of all, install Node.js, you can download it in the oficial web site, an after that, open your terminal and run the following command to check the version (your version may vary, this was the version I got)

$ node -v
$ v9.5.0

next, you need to create a new folder to your project

mkdir api_test
cd api_test

Once in the folder, initialise the project

npm init

It's possible to provide the information about the project, but I will let all the default information, in the end type yes to conclude the process and create the package.json file.

The package.json content should be something like this

If you are not familiar with package.json , this file holds all dependency references used by our software, helping other developers to install and run it in an "automagic way".

Now its time to install the items we need to proceed with the tests

npm install mocha -g --save-dev
npm install chai --save-dev
npm install should --save-dev
npm install request --save-dev

The installed packages are:

• Mocha — Test Framework
• Chai — Test Framework
• Should — Library to extend the tests
• Request — To execute API calls

At this moment, all dependencies are stored inside package.json and a new folder called node_modules was created.

Project folder structure

Mocha runs the tests automatically since the files are inside the folder test, so lets create it

mkdir test

What are we going to test?

We are going to use an API that returns info about the card game Magic the Gathering (which I like a lot).

That is a REST FULL API, so we will be able to test a various test scenarios, which is great to learn the concepts (but just to be aligned, this tutorial is just an entry point, the limits are up to you)

Writing the test case

Using your favorite text editor (mine is VS Code), let's create our first test case.

As I said earlier, mocha runs any file inside the folder test, so, let's create our first test case, to do that, we need to create a file called card.spec.js, with the following structure.

Running

To run the tests, we just need to execute the following command in the project's root folder:

mocha

The test result will be like bellow (success case)

Simulating an error (compares 400 with 200 in the test result) we will get the error:

Finalising

For sure there a lot of other functions details of Chai, but this post is just to get the basic needed structure to create your tests

Take a look in the code comments, they will help you and also the Chai's documentation is really good

The project can be downloaded on GITHUB.

h3nr1ke/teste_api

If you want to talk to me regarding Node or Magic, send me a message on twitter, and if you are looking a good place to host your apps, click here and get USD100 to test =).

Photo by Glenn Carstens-Peters on Unsplash