Property-based testing helps you create better, more solid tests with little code. By using the PropEr framework in both Erlang and Elixir, this book teaches you how to automatically generate test cases, test stateful programs, and change how you design your software for more principled and reliable approaches. You will be able to better explore the problem space, validate the assumptions you make when coming up with program behavior, and expose unexpected weaknesses in your design. PropEr will even show you how to reproduce the bugs it found. With this book, you will be writing efficient property-based tests in no time. Most tests only demonstrate that the code behaves how the developer expected it to behave, and therefore carry the same blind spots as their authors when special conditions or edge cases show up. Learn how to see things differently with property tests written in PropEr. Start with the basics of property tests, such as writing stateless properties, and using the default generators to generate test cases automatically. More importantly, learn how to think in properties. Improve your properties, write custom data generators, and discover what your code can or cannot do. Learn when to use property tests and when to stick with example tests with real-world sample projects. Explore various testing approaches to find the one that's best for your code. Shrink failing test cases to their simpler expression to highlight exactly what breaks in your code, and generate highly relevant data through targeted properties. Uncover the trickiest bugs you can think of with nearly no code at all with two special types of properties based on state transitions and finite state machines. Write Erlang and Elixir properties that generate the most effective tests you'll see, whether they are unit tests or complex integration and system tests. What You Need Basic knowledge of Erlang, optionally ElixirFor Erlang tests: Erlang/OTP >= 20.0, with Rebar >= 3.4.0For Elixir tests: Erlang/OTP >= 20.0, Elixir >= 1.5.0

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.

Don't accept the compromise between fast and beautiful: you can have it all. Phoenix creator Chris McCord, Elixir creator Jose Valim, and award-winning author Bruce Tate walk you through building an application that's fast and reliable. At every step, you'll learn from the Phoenix creators not just what to do, but why. Packed with insider insights, this definitive guide will be your constant companion in your journey from Phoenix novice to expert, as you build the next generation of web applications. Phoenix is the long-awaited web framework based on Elixir, the highly concurrent language that combines a beautiful syntax with rich metaprogramming. The authors, who developed the earliest production Phoenix applications, will show you how to create code that's easier to write, test, understand, and maintain. The best way to learn Phoenix is to code, and you'll get to attack some interesting problems. Start working with controllers, views, and templates within the first few pages. Build an in-memory repository, and then back it with an Ecto database layer. Learn to use change sets and constraints that keep readers informed and your database integrity intact. Craft your own interactive application based on the channels API for the real-time, high-performance applications that this ecosystem made famous. Write your own authentication components called plugs, and even learn to use the OTP layer for monitored, reliable services. Organize your code with umbrella projects so you can keep your applications modular and easy to maintain. This is a book by developers and for developers, and we know how to help you ramp up quickly. Any book can tell you what to do. When you've finished this one, you'll also know why to do it. What You Need: To work through this book, you will need a computer capable of running Erlang 17 or better, Elixir 1.1, or better, Phoenix 1.0 or better, and Ecto 1.0 or better. A rudimentary knowledge of Elixir is also highly recommended.

Languages may come and go, but the relational database endures. Learn how to use Ecto, the premier database library for Elixir, to connect your Elixir and Phoenix apps to databases. Get a firm handle on Ecto fundamentals with a module-by-module tour of the critical parts of Ecto. Then move on to more advanced topics and advice on best practices with a series of recipes that provide clear, step-by-step instructions on scenarios commonly encountered by app developers. Co-authored by the creator of Ecto, this title provides all the essentials you need to use Ecto effectively. Elixir and Phoenix are taking the application development world by storm, and Ecto, the database library that ships with Phoenix, is going right along with them. There are plenty of examples that show you the basics, but to use Ecto to its full potential, you need to learn the library from the ground up. This definitive guide starts with a tour of the core features of Ecto - repos, queries, schemas, changesets, transactions - gradually building your knowledge with tasks of ever-increasing complexity. Along the way, you'll be learning by doing - a sample application handles all the boilerplate so you can focus on getting Ecto into your fingers. Build on that core knowledge with a series of recipes featuring more advanced topics. Change your pooling strategy to maximize your database's efficiency. Use nested associations to handle complex table relationships. Add streams to handle large result sets with ease. Based on questions from Ecto users, these recipes cover the most common situations developers run into. Whether you're new to Ecto, or already have an app in production, this title will give you a deeper understanding of how Ecto works, and help make your database code cleaner and more efficient. What You Need: To follow along with the book, you should have Erlang/OTP 19+ and Elixir 1.4+ installed. The book will guide you through setting up a sample application that integrates Ecto.

Give users the real-time experience they expect, by using Elixir and Phoenix Channels to build applications that instantly react to changes and reflect the application's true state. Learn how Elixir and Phoenix make it easy and enjoyable to create real-time applications that scale to a large number of users. Apply system design and development best practices to create applications that are easy to maintain. Gain confidence by learning how to break your applications before your users do. Deploy applications with minimized resource use and maximized performance. Real-time applications come with real challenges - persistent connections, multi-server deployment, and strict performance requirements are just a few. Don't try to solve these challenges by yourself - use a framework that handles them for you. Elixir and Phoenix Channels provide a solid foundation on which to build stable and scalable real-time applications. Build applications that thrive for years to come with the best-practices found in this book. Understand the magic of real-time communication by inspecting the WebSocket protocol in action. Avoid performance pitfalls early in the development lifecycle with a catalog of common problems and their solutions. Leverage GenStage to build a data pipeline that improves scalability. Break your application before your users do and confidently deploy them. Build a real-world project using solid application design and testing practices that help make future changes a breeze. Create distributed apps that can scale to many users with tools like Phoenix Tracker. Deploy and monitor your application with confidence and reduce outages. Deliver an exceptional real-time experience to your users, with easy maintenance, reduced operational costs, and maximized performance, using Elixir and Phoenix Channels. What You Need: You'll need Elixir 1.9+ and Erlang/OTP 22+ installed on a Mac OS X, Linux, or Windows machine.

Summary The Little Elixir & OTP Guidebook gets you started programming applications with Elixir and OTP. You begin with a quick overview of the Elixir language syntax, along with just enough functional programming to use it effectively. Then, you'll dive straight into OTP and learn how it helps you build scalable, fault-tolerant and distributed applications through several fun examples. Purchase of the print book includes a free eBook in PDF, Kindle, and ePub formats from Manning Publications. About the Technology Elixir is an elegant programming language that combines the expressiveness of Ruby with the concurrency and fault-tolerance of Erlang. It makes full use of Erlang's BEAM VM and OTP library, so you get two decades' worth of maturity and reliability right out of the gate. Elixir's support for functional programming makes it perfect for modern event-driven applications. About the Book The Little Elixir & OTP Guidebook gets you started writing applications with Elixir and OTP. You'll begin with the immediately comfortable Elixir language syntax, along with just enough functional programming to use it effectively. Then, you'll dive straight into several lighthearted examples that teach you to take advantage of the incredible functionality built into the OTP library. What's Inside Covers Elixir 1.2 and 1.3 Introduction to functional concurrency with actors Experience the awesome power of Erlang and OTP About the Reader Written for readers comfortable with a standard programming language like Ruby, Java, or Python. FP experience is helpful but not required. About the Author Benjamin Tan Wei Hao is a software engineer at Pivotal Labs, Singapore. He is also an author, a speaker, and an early adopter of Elixir. Table of Contents GETTING STARTED WITH ELIXIR AND OTP Introduction A whirlwind tour Processes 101 Writing server applications with GenServer FAULT TOLERANCE, SUPERVISION, AND DISTRIBUTION Concurrent error-handling and fault tolerance with links, monitors, and processes Fault tolerance with Supervisors Completing the worker-pool application Distribution and load balancing Distribution and fault tolerance Dialyzer and type specifications Property-based and concurrency testing