How to scaffold ExpressJS server and test it

The absolute basics.

Photo by Danielle MacInnes on Unsplash

This is part 1 of multi-part series on express API.

Introduction

Express website introduces thusly—

Express is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications.

But what is Node.js ? Glad you asked!

Node.js is an open-source, cross-platform, JavaScript runtime environment that executes JavaScript code outside a web browser. Node.js lets developers use JavaScript to write command line tools and for server-side scripting — running scripts server-side to produce dynamic web page content before the page is sent to the user’s web browser.

Simply put —

Node.js allows javascript to run outside of browser, thus allowing us to create a server using JS.

Express is a framework based on Node.js and adds more functionality and makes it easier for us to create a server.

Enough talk, Let’s Start!

(Before we really start, make sure you have node installed already

node --version , else install it from here)

• Create a new folder which will hold our code —

mkdir express-demo && cd express-demo

• (Optionally) Initialize git for version control and add a .gitignore file —

git init

touch .gitignore

Add node_modules and .env to .gitignore

After this basic setup, time to go after it!

• Create a package.json file in the folder by

npm init -y .

This will skip the interactive process for npm init and create a basic package.json file in the root folder.

Time to install dependencies —

We will use npm install or npm i to get the packages from npm registry and install them in our app.

• Start with the big one first!

npm i express

• We add another useful package

npm i dotenv

Dotenv package allows us to store and access valuable private information like credentials securely and easily.

• Some more packages

npm i — save-dev morgan nodemon

Morgan logs the network requests received by our API, and we can decide what details we need to see in the log.

Nodemon keeps the API running with updated code, every time we change something. So it always keeps the latest API available for us.

Now we have requisite packages to start writing our code.

• Create src folder and add app.js in it.

mkdir src

touch src/app.js

• Create a .env file to hold our environmental variables.

touch .env

Add the desired port to .env

• Add a command start to package.json —

“start”: “nodemon ./src/app.js”

• Update app.js with following code —

Here we use dotenv to fetch the port from .env file and use it.

We require express and scaffold a server called app . To keep the server running, we need app to listen on the 3000 port for any incoming network requests.

Enough coding, let’s see it in action already!

Run npm run start on your terminal and you will see App listening on port 3000

nodemon running successfully in terminal

Time to add other dependencies, (or middlewares) to app.js which will now look like this —

Make sure you see App listening on port 3000 still on the terminal.

You have now successfully scaffolded an express API.

There is, however, no way to actually reach the API we just built. For that, we need to add endpoints to our API where clients can reach out and interact.

We will add GET /posts route first.

Adding a route to our app

• Add a routes folder inside /src folder and add posts.js to it.

mkdir src/routes

touch src/routes/posts.js

We will use express router to set up our routes.

And we need to import it in app.js to use it.

Now (assuming your nodemon is still running in terminal) if you visit localhost:3000/posts in your browser, you will see You have hit GET /posts endpoint in the tab.

You can see the response in browser

You will also see GET /posts 200 2.252 ms — 32 in your nodemon log.

Instead of sending a string as response, we can send a JSON object as well.

Testing our app

As our app grows, it becomes important to make sure the functionality is working as intended. Automated testing is a fantastic tool for that.

• To test our implementation, we will use mocha as test framework, and chai and supertest as helpers.

npm i — save-dev chai mocha supertest

• Add a configuration file for mocha — touch .mocharc.json

• Update “test” script in package.json with

”test”: “NODE_ENV=test NODE_NO_WARNINGS=1 mocha”

We will also add module.exports = app at the bottom of our app.js file to make it accessible to mocha.

• Create a test folder and add posts.spec.js file in it —

mkdir test

touch test/posts.spec.js .

Add the following code to it —

• Run the test

npm run test

It will go green!

In the next part, we will look at setting up database and connecting our API with it to persist data.

Here is Part 2.

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