Testing
Snapshot testing captures a rendered view as a reference image, then on every subsequent test run it re-renders the same view and compares the result pixel by pixel. Any mismatch—a font change, a shifted layout, an unexpected color—fails the test immediately and shows you a diff image.
Mobile Testing
Mobile teams constantly fight the same battle: test code for iOS and Android is 80% identical but diverges on selectors, gestures, permission dialogs, and platform-specific behaviors. The naive approach is two separate test suites. The right approach is shared test logic with platform adapters. This guide covers the architectural
Appium
Appium's XCUITest driver wraps Apple's XCUITest framework, which means iOS automation runs through the same testing infrastructure that Xcode uses natively.
Swift
XCTest includes a built-in performance testing API that lets you measure how long a block of code takes and compare it against a stored baseline.
Swift
Instruments is Apple's performance analysis tool included with Xcode. It attaches to a running process — including your test target — and records CPU usage, memory allocations, and retain cycles. When tests run slowly or your app leaks memory during a test run, Instruments shows you exactly where the time
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
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
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,
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
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.
Maestro
Maestro is a mobile testing framework that replaces imperative test code with declarative YAML flows. You describe what the user does — tap this, type that, assert visible — and Maestro handles synchronization, retries, and cross-platform execution. This guide covers the flow syntax, handling dynamic content, CI integration, and how Maestro
Detox
End-to-end testing of mobile apps has historically been plagued by flakiness. Tests that pass locally fail in CI.