Swift
Mocking in Swift revolves around one idea: hide concrete implementations behind protocols so tests can swap in controlled fakes. This guide covers three levels of sophistication—manual mocks, Mockingbird's generated mocks, and Sourcery templates—so you can choose the right tool for your project. Why Protocols Enable Mocking
Testing
Swift Package Manager is the standard way to distribute reusable Swift code — networking libraries, analytics SDKs, UI components. But SPM packages are often distributed without tests, or with tests that can't run outside the original developer's environment. This guide covers how to structure testable Swift packages,
Testing
Swift macros (introduced in Xcode 15 / Swift 5.9) transform code at compile time. But how do you test them? Testing a macro means testing code transformation — given this input syntax, does the macro produce the expected output syntax? Apple's SwiftSyntaxMacrosTestSupport library and Point-Free's MacroTesting
Swift
Concurrency transformed Swift development, but it also introduced new testing challenges. How do you assert on values that arrive asynchronously? How do you test @MainActor-isolated code? This guide covers every pattern you'll need. Async Test Functions in XCTest XCTest supports async test functions natively since Xcode 13.
Testing
macOS AppKit applications are tested with XCTest, Apple's first-party testing framework.
Swift
watchOS apps have the same Xcode testing infrastructure as iOS — XCTest, the test report, and CI integration all work.
Swift
tvOS apps run on Apple TV, where the primary input is a Siri Remote rather than a touchscreen.
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
Swift
visionOS is Apple's operating system for Apple Vision Pro. It runs SwiftUI apps in an immersive spatial environment alongside traditional window-based apps.
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
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,