Elixir offers new paradigms, and challenges you to test in unconventional ways. Start with ExUnit: almost everything you need to write tests covering all levels of detail, from unit to integration, but only if you know how to use it to the fullest - we'll show you how. Explore testing Elixir-specific challenges such as OTP-based modules, asynchronous code, Ecto-based applications, and Phoenix applications. Explore new tools like Mox for mocks and StreamData for property-based testing. Armed with this knowledge, you can create test suites that add value to your production cycle and guard you from regressions.
Write Elixir tests that you can be proud of. Dive into Elixir's test philosophy and gain mastery over the terminology and concepts that underlie good tests. Create and structure a comprehensive ExUnit test suite, starting from the basics, and build comprehensive test coverage that will provide safety for refactoring and confidence that your code performs as designed. Use tests to make your software more reliable and fault tolerant.
Explore the basic tool set provided by ExUnit and Mix to write and organize your test suite. Test code built around different OTP functionality. Isolate your code through dependency injection and by using Mox. Write comprehensive tests for Ecto projects, covering Ecto as a database tool as well as a standalone data validation tool. Test Phoenix channels from end to end, including authentication and joining topics. Write Phoenix controller tests and understand the concepts of integration testing in Elixir. Learn property-based testing with StreamData from the author who wrote the library.
Code with high confidence that you are getting the most out of your test suite, with the right tools that make testing your code a pleasure and a valuable part of your development cycle.
What You Need:
To get the most out of this book, you will need to have installed Elixir 1.8 or later and Erlang/OTP 21 or later. In order to complete the relevant chapters, you will also need Ecto 3.1 or later, EctoSQL 3.1 or later and Phoenix 1.3 or later.
Author(s): Andrea Leopardi, Jeffrey Matthias
Edition: 1
Publisher: Pragmatic Bookshelf
Year: 2021
Language: English
Pages: 264
Tags: Testing; Test Framework; Test Suite;
Cover
Table of Contents
Acknowledgments
Andrea Leopardi
Jeffrey Matthias
Introduction
Why Do We Need a Book for Testing in Elixir?
Who This Book Is For
How to Read This Book
About the Code
Online Resources
1. Unit Tests
Defining the Unit in Unit Test
Testing with ExUnit
Organizing Your Tests
Creating Comprehensive Test Coverage
Testing Pure Functions
Refactoring Toward Pure Functions
Isolating Code
Wrapping Up
2. Integration and End-to-End Tests
What Is an Integration Test?
Testing Against Real External Dependencies
Dependency Doubles
Interfacing to External Dependencies with Behaviours
Test Doubles: Stubs, Mocks, and Fakes
The Hidden Benefits of Dependency Doubles
Testing the Actual Interaction with Services
End-to-End Tests
Wrapping Up
3. Testing OTP
Testing a GenServer
Controlling the Life Cycle of OTP Processes in Tests
Testing Periodic Actions
Testing Singleton Resources
Testing Resiliency
Wrapping Up
4. Testing Ecto Schemas
Testing Your Schema Through Changesets
Refactoring to Increase Test Maintainability
Creating a SchemaCase for Shared Test Code
Testing an Ecto Schema as a Data Validator
Testing an Ecto Schema for Database Interactions
Testing Your Schema Through Database Calls
Setting Up Sandbox Mode
Wrapping Up
5. Testing Ecto Queries
Creating a Factory to Help with Setup
Adding a DataCase to Help with Setup
Testing Create
Testing Read
Testing Update
Testing Delete
Wrapping Up
6. Testing Phoenix
The Role of Phoenix in Your Application
Testing JSON-Based APIs
Testing Server-Rendered HTML Applications
Testing Phoenix Channels
Wrapping Up
7. Property-Based Testing
Property-Based Testing in Practice in the Elixir Standard Library
Example-Based Tests
Introducing Randomness and Property-Based Testing
Data Generation
Writing Properties
Shrinking
Strategies for Designing Properties
Stateful Property-Based Testing
Wrapping Up
A1. When To Randomize Test Data
A2. Test Life Cycle
The Life Cycle of an ExUnit Suite
Test Cases
Executing Tests
An Example and a Drawing
A3. Test Coverage
Built-In Test Coverage
Coveralls and the Excoveralls Library
Bibliography
Index
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