Book Image

TypeScript 2.x By Example

By : Sachin Ohri
Book Image

TypeScript 2.x By Example

By: Sachin Ohri

Overview of this book

The TypeScript language, compiler, and open source development toolset brings JavaScript development up to the enterprise level. It allows you to use ES5, ES6, and ES7 JavaScript language features today, including classes, interfaces, generics, modules, and more. Its simple typing syntax enables building large, robust applications using object-oriented techniques and industry-standard design principles. This book aims at teaching you how to get up and running with TypeScript development in the most practical way possible. Taking you through two exciting projects built from scratch, you will learn the basics of TypeScript, before progressing to functions, generics, promises, and callbacks. Then, you’ll get to implement object-oriented programming as well as optimize your applications with effective memory management. You’ll also learn to test and secure your applications, before deploying them. Starting with a basic SPA built using Angular, you will progress on to building, maybe, a Chat application or a cool application. You’ll also learn how to use NativeScript to build a cool mobile application. Each of these applications with be explained in detail, allowing you to grasp the concepts fast. By the end of this book, you will have not only built two amazing projects but you will also have the skills necessary to take your development to the next level.
Table of Contents (11 chapters)

Writing test cases for the services class

Next up, let's look at our service class, and see how we can write a test for it. Every project you work on that will require data from some other system will have a service class, which will be using HTTP to make the web service call.

So, if we want to write a unit test for our service class, we would need to mock the HTTP and any other external dependencies our service class would have.

Creating a new file

Let's first create a new file, trello.service.spec.ts, in our services folder. All our test cases for the Trello service will be written in this file.

Our Trello service has only one function right now, that is, to fetch the boards from the JSON file using the HTTP...