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. Where Phoenix.LiveViewTest tests the server side without a browser, Wallaby tests the complete stack — JavaScript execution, CSS animations, WebSocket connections, and real browser rendering. It's the closest you get to testing what users actually
Elixir
ExUnit is Elixir's built-in test framework. Most guides cover the basics — assert, refute, describe. But ExUnit has powerful features that separate good test suites from great ones: tags for selective execution, doctests that keep documentation accurate, async execution for faster runs, and custom assertions that make failures
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. Bypass spins up a real HTTP server locally, intercepts requests your application makes, and lets you define exactly what responses to return. Unlike request-level stubs, Bypass tests your HTTP
Testing
Phoenix.LiveViewTest and Phoenix.ConnTest test your application logic without a browser. For acceptance tests that verify the full user experience — JavaScript behavior, CSS-driven interactions, and visual rendering — you need real browser automation. Wallaby provides this for Elixir, integrating tightly with ExUnit and supporting concurrent test execution. What Wallaby
Testing
Phoenix applications expose their behavior through HTTP endpoints. Testing these endpoints — verifying correct status codes, response bodies, redirects, and authentication — is essential for confident Phoenix development. Phoenix.ConnTest provides exactly this capability, letting you exercise your controllers without starting an actual HTTP server. What Phoenix.ConnTest Does Phoenix.ConnTest builds
Testing
Phoenix LiveView enables rich, real-time web interfaces without writing JavaScript. Testing LiveView requires a different approach than traditional controller tests because LiveView components are stateful, event-driven, and update asynchronously. The Phoenix.LiveViewTest module provides the tools to test these interactions deterministically. How LiveView Testing Works Phoenix.LiveViewTest mounts
Testing
Example-based tests verify specific cases: given input A, expect output B. Property-based tests verify invariants: for any input from this domain, some relationship must hold. You write fewer tests and cover far more ground. StreamData is Elixir's answer to QuickCheck and Hypothesis. It ships with a
Testing
Elixir ships with a built-in testing framework called ExUnit. Unlike many languages where testing frameworks are third-party add-ons, ExUnit is part of the Elixir standard library and is the default choice for testing Elixir applications. This guide covers everything you need to write effective tests from day
Testing
Testing code that calls external services — payment processors, email providers, third-party APIs — presents a challenge. You don't want real network calls in your test suite, but you also don't want to lose confidence in how your code handles those interactions. Mox, Elixir's standard