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

Unit testing

Unit testing refers to when you want to test a specific method, whether it be on the top level or as part of an object, in isolation. Testing it in isolation is an important part of this type of testing. Doing this ensures that you are only testing the logic you want and not the logic of its dependencies.

Crystal comes bundled with the Spec module, which provides the tools required to test your code. For example, say you have the following method that returns the sum of two values as part of add.cr:

def add(value1, value2)
  value1 + value2
end

The related tests for this could look like this:

require "spec"
require "./add"
 
describe "#add" do
  it "adds with positive values" do
    add(1, 2).should eq 3
  end
 
  it "adds with negative values" do
    add(-1, -2).should eq -3
  end
 
  it "adds with mixed...