Book Image

Crystal Programming

By : George Dietrich, Guilherme Bernal
Book Image

Crystal Programming

By: George Dietrich, Guilherme Bernal

Overview of this book

Crystal is a programming language with a concise and user-friendly syntax, along with a seamless system and a performant core, reaching C-like speed. This book will help you gain a deep understanding of the fundamental concepts of Crystal and show you how to apply them to create various types of applications. This book comes packed with step-by-step explanations of essential concepts and practical examples. You'll learn how to use Crystal’s features to create complex and organized projects relying on OOP and its most common design patterns. As you progress, you'll gain a solid understanding of both the basic and advanced features of Crystal. This will enable you to build any application, including command-line interface (CLI) programs and web applications using IOs, concurrency and C bindings, HTTP servers, and the JSON API. By the end of this programming book, you’ll be equipped with the skills you need to use Crystal programming for building and understanding any application you come across.
Table of Contents (26 chapters)
1
Part 1: Getting Started
5
Part 2: Learning by Doing – CLI
10
Part 3: Learn by Doing – Web Application
13
Part 4: Metaprogramming
18
Part 5: Supporting Tools

Why test?

Within both of the two larger projects we worked through so far, and all of the other examples, we have been manually running them after changes were made to ensure they produced the expected output, such as returning the correct response, producing the desired transformation, or simply printing the correct value to the terminal.

This process is fine when there are only a handful of methods/flows. However, as the application grows, it can become infeasible to test each method or flow on its own after every change. Granted—you could revert to only testing things directly related to what you changed, but this could lead to missed bugs within other logic that makes use of it. Testing is a process of writing additional code that makes assertions in an automated fashion to ensure the code executes as expected.

Testing can also be a good way to ensure no that a change does not result in unintentionally breaking public application programming interface (API) of your...