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 meaningful.
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 client configuration,
Ruby
Basic Capybara usage covers maybe 70% of test scenarios. The remaining 30% involves complex browser behaviors: embedded iframes, file downloads, multiple authenticated sessions, custom wait conditions, and browser-specific configuration. This guide covers those advanced patterns. JavaScript Driver Configuration Capybara supports multiple JavaScript drivers. Choosing the right one affects test speed,
Scala
Testing cats-effect applications requires a test framework that understands IO. Running IO in tests naively—calling .unsafeRunSync()—works but loses meaningful error messages, leaks resources, and breaks in concurrent scenarios. munit-cats-effect provides native IO support for MUnit, making tests composable and resource-safe. This guide covers munit-cats-effect setup, testing IO computations,
Scala
Akka actors are concurrent by nature — they communicate asynchronously through message passing, which makes traditional unit testing approaches fail. akka-testkit provides TestKit and TestProbe to write deterministic tests for actor behavior: message routing, state transitions, supervision strategies, and timing. This guide covers the classic Akka (untyped) testkit and Akka Typed&
iOS
Apple's swift-testing framework (available in Xcode 16, Swift 6) replaces XCTest's 20-year-old Objective-C heritage with a modern, macro-based API. Instead of XCTAssertEqual, you write #expect(a == b). Instead of func testSomething(), you write @Test func something(). Parameterized tests, parallel execution, and expressive failure messages are built
iOS
Running xcodebuild test directly gives you raw XML logs, cryptic failures, and no easy way to integrate results into your CI pipeline. Fastlane's scan action wraps xcodebuild with sensible defaults, human-readable output, JUnit XML for CI consumption, HTML reports, and built-in Slack notifications. This guide covers scheme configuration,
iOS
Realm's object graph persistence is tightly coupled to its runtime — you can't just pass in a mock dictionary. Testing Realm-backed iOS code requires either an in-memory Realm configuration (fast, isolated, no file cleanup) or a purpose-built mock layer. This guide covers both approaches, plus migration testing,
iOS
Combine's asynchronous, declarative model makes testing tricky — pipelines emit values over time, operators transform them, and errors can cancel the stream. This guide covers two approaches: the built-in XCTestExpectation pattern for simple cases, and the CombineExpectations library for ergonomic, readable publisher assertions. You'll write tests for
iOS
XCUITest runs your app in a simulator — it's slow, flaky, and gives no introspection into SwiftUI internals. ViewInspector lets you unit test SwiftUI views directly: inspect the view hierarchy, find subviews by type, trigger bindings, simulate button taps, and assert on text values — all without launching a simulator.
Testing
NBomber is a load testing framework for .NET that lets you define scenarios and load shapes in C#, run them programmatically, and get structured statistics — making it natural to integrate load tests into a .NET project without learning a separate DSL. Key Takeaways * Scenarios are defined as C# code using