Book Image

Mastering Elixir

By : André Albuquerque, Daniel Caixinha
Book Image

Mastering Elixir

By: André Albuquerque, Daniel Caixinha

Overview of this book

Running concurrent, fault-tolerant applications that scale is a very demanding responsibility. After learning the abstractions that Elixir gives us, developers are able to build such applications with inconceivable low effort. There is a big gap between playing around with Elixir and running it in production, serving live requests. This book will help you fll this gap by going into detail on several aspects of how Elixir works and showing concrete examples of how to apply the concepts learned to a fully ?edged application. In this book, you will learn how to build a rock-solid application, beginning by using Mix to create a new project. Then you will learn how the use of Erlang's OTP, along with the Elixir abstractions that run on top of it (such as GenServer and GenStage), that allow you to build applications that are easy to parallelize and distribute. You will also master supervisors (and supervision trees), and comprehend how they are the basis for building fault-tolerant applications. Then you will use Phoenix to create a web interface for your application. Upon fnishing implementation, you will learn how to take your application to the cloud, using Kubernetes to automatically deploy, scale, and manage it. Last, but not least, you will keep your peace of mind by learning how to thoroughly test and then monitor your application.
Table of Contents (18 chapters)
Title Page
Dedication
Packt Upsell
Contributors
Preface
5
Demand-Driven Processing
Index

Testing macros


In this section, we'll be checking out how to create tests for macros. Particularly, we'll be adding a test for the defchrono macro that we created in Chapter 6, Metaprogramming – Code that Writes Itself. Like the last section, where we added tests for our Phoenix Channels, this section isn't related to a type of testing, but rather related with showing how to test a particular component we've created.

 

The most common and effective approach to test macros is to assert on the behavior of the code generated by the macro, and not on the code generation itself. Testing the generated AST directly often leads to brittle and unmanageable tests. These tests can be seen as unit tests for macros, because they're testing the macro expansion itself. Our focus should be on integration tests for macros. This means that we'll create a test module, with the sole purpose of calling use on our macro, and then place assertions on this test module. Let's check the code for this test:

$ cat apps...