Book Image

Building Enterprise JavaScript Applications

By : Daniel Li
Book Image

Building Enterprise JavaScript Applications

By: Daniel Li

Overview of this book

With the over-abundance of tools in the JavaScript ecosystem, it's easy to feel lost. Build tools, package managers, loaders, bundlers, linters, compilers, transpilers, typecheckers - how do you make sense of it all? In this book, we will build a simple API and React application from scratch. We begin by setting up our development environment using Git, yarn, Babel, and ESLint. Then, we will use Express, Elasticsearch and JSON Web Tokens (JWTs) to build a stateless API service. For the front-end, we will use React, Redux, and Webpack. A central theme in the book is maintaining code quality. As such, we will enforce a Test-Driven Development (TDD) process using Selenium, Cucumber, Mocha, Sinon, and Istanbul. As we progress through the book, the focus will shift towards automation and infrastructure. You will learn to work with Continuous Integration (CI) servers like Jenkins, deploying services inside Docker containers, and run them on Kubernetes. By following this book, you would gain the skills needed to build robust, production-ready applications.
Table of Contents (26 chapters)
Title Page
Copyright and Credits
Dedication
Packt Upsell
Contributors
Preface
Free Chapter
1
The Importance of Good Code
Index

Writing our first unit test


Let's write unit tests for the generateValidationErrorMessage function. But first, let's convert our src/validators/errors/messages.js file into its own directory so that we can group the implementation and test code together in the same directory:

$ cd src/validators/errors
$ mkdir messages
$ mv messages.js messages/index.js
$ touch messages/index.unit.test.js

Next, in index.unit.test.js, import the assert library and our index.js file:

import assert from 'assert';
import generateValidationErrorMessage from '.';

Now, we are ready to write our tests.

Describing the expected behavior

When we installed the mocha npm package, it provided us with the mocha command to execute our tests. When we run mocha, it will inject several functions, including describe and it, as global variables into the test environment. The describe function allows us to group relevant test cases together, and the it function defines the actual test case.

Inside index.unit.tests.js, let's define our...