Testing
Jetpack Compose has its own testing APIs that don't use Espresso's view matchers. Instead, Compose tests work against the semantics tree — an accessibility-oriented representation of your UI that's separate from the rendering layer. This makes Compose tests faster and less brittle than Espresso tests
Testing
Robolectric runs Android tests on the JVM — no emulator, no device, no waiting for adb to connect. It implements Android's framework classes as JVM-compatible stubs, so your Activities, Fragments, ViewModels, and Repositories run in a regular JUnit test process. A Robolectric test suite that takes 30 seconds to
Testing
App performance isn't tested — it's measured. Android's Macrobenchmark library gives you a framework for measuring startup time, frame rendering, and custom interactions on real devices. Baseline Profiles use those measurements to pre-compile critical code paths, and Perfetto lets you trace exactly what's
Scala
ZIO Test is the native testing framework for ZIO applications. It integrates deeply with ZIO's effect system, giving you precise control over concurrency, timing, and resource management in tests. Unlike JUnit or ScalaTest, ZIO Test treats tests as effects — first-class ZIO values that compose, retry, and parallelize naturally.
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
Ruby
Tests that make real HTTP requests are slow, flaky, and dependent on external services staying available. VCR and WebMock solve this by intercepting HTTP requests and either returning pre-recorded responses or raising errors when unexpected network calls happen. This guide covers both tools, when to use each, and how to
Ruby
Rails system tests let you test your application through a real browser, exercising JavaScript, authentication flows, and multi-step user interactions that unit tests cannot reach. They use Capybara as the test DSL and Selenium WebDriver to control Chrome or Firefox. This guide covers writing effective system tests, handling JavaScript interactions,
Ruby
Rails APIs need a different testing approach than HTML applications. There's no browser to drive, no UI interactions — just HTTP requests and JSON responses. RSpec request specs are the right tool: they test the full request/response cycle through Rack middleware without the overhead of a browser. This
Ruby
Minitest ships with Ruby's standard library and powers the default test suite in every new Rails application. It's fast, minimal, and surprisingly capable. Many teams that start with RSpec eventually migrate back to Minitest for its simplicity and performance. This guide covers everything you need to
Elixir
Phoenix LiveView testing uses Phoenix.LiveViewTest to render LiveViews server-side and simulate user interactions without a browser. Tests run fast — no Selenium, no ChromeDriver — while still testing the full LiveView lifecycle: mount, events, component updates, and live navigation. This guide covers testing LiveViews and LiveComponents, simulating JS hook interactions, testing
Scala
Apache Pekko is the community-maintained fork of Akka (post-BSL license change). Its testing API mirrors Akka's closely, with the same ActorTestKit, BehaviorTestKit, and TestProbe tools — making migration from Akka to Pekko straightforward. This guide focuses on Pekko Typed actor testing patterns. Setup // build.sbt libraryDependencies ++= Seq( "org.
Scala
http4s is a purely functional HTTP library for Scala built on cats-effect. Its route handlers are values — HttpRoutes[F] is just a function from Request[F] to OptionT[F, Response[F]]. This makes testing routes trivial: construct a request, run it through the routes, inspect the response — all without starting