Testing
Phoenix applications are testable by design. The framework ships with first-class testing support built on ExUnit, Elixir's built-in test framework. Controllers, channels, LiveView components, and database interactions all have purpose-built test helpers. This guide covers the full picture. Project Structure A freshly generated Phoenix project
Testing
ExUnit ships with Elixir. No install, no configuration file to bootstrap, no framework ceremony. You write a module, use ExUnit.Case, and run mix test. That simplicity is intentional — the Elixir team treats testing as a first-class citizen, not an afterthought. This guide covers everything you need to write
Elixir
ExUnit ships with everything you need for production-grade Elixir testing, but most developers only scratch the surface. This post covers setup/teardown, tags, async safety, custom assertions, doctests, and isolation patterns that keep large test suites fast and reliable. ExUnit is Elixir's built-in test framework, and
Testing
mix test is the entry point for all Elixir testing. While ExUnit handles test structure and assertions, mix test controls how tests are discovered, filtered, and executed. This guide covers the configuration knobs that matter most in production Elixir projects — from test tagging to coverage reporting to CI pipeline setup.
Testing
Testing Elixir applications that use Ecto requires understanding one core mechanism: the SQL sandbox. Get it right, and you can run hundreds of database tests in parallel with full isolation. Get it wrong, and you have flaky tests that pass individually but fail when run together. This guide covers the
Property-Based Testing
PropEr is the open-source property-based testing library for Erlang, directly inspired by Quviq's commercial QuickCheck. It brings full stateful testing, type-based generation, and targeted property-based testing (TPBT) to the Erlang/OTP ecosystem. For Elixir, PropEr integrates with ExUnit via the PropCheck library. Why PropEr
Elixir
Property-based testing generates hundreds of random inputs and finds edge cases you would never think to write by hand. This post covers StreamData generators, the ExUnitProperties module, how shrinking works, and techniques for composing generators to describe realistic domain data. Example-based tests are assertions about specific inputs you
Elixir
Phoenix LiveView's test module gives you a full server-side rendering environment without a browser. This post covers mounting views, simulating user interactions, testing navigation, form submission, JS hook callbacks, and real-time push events — all in fast, deterministic ExUnit tests. LiveView moved the rendering loop to the
Elixir
Wallaby is an Elixir browser testing library that drives real browsers through WebDriver.
Elixir
ExUnit is Elixir's built-in test framework. Most guides cover the basics — assert, refute, describe.
Elixir
Excoveralls generates test coverage reports for Elixir projects. It integrates with Coveralls.io for PR coverage comments, generates HTML reports for local review, and produces LCOV format for other coverage tools. Setting up coverage reporting early helps maintain quality as your Phoenix application grows. Installation # mix.exs def project do
Elixir
When Elixir applications call external HTTP services — payment processors, webhooks, third-party APIs — tests need to control those HTTP interactions.