hboon

The Ultimate Swift Testing Playbook (2024 WWDC Edition, expanded with Apple docs from June 2025)

Updated with info from https://developer.apple.com/documentation/testing fetched via Firecrawl on June 7, 2025.

See also my blog: See also my blog post: https://steipete.me/posts/2025/migrating-700-tests-to-swift-testing

A hands-on, comprehensive guide for migrating from XCTest to Swift Testing and mastering the new framework. This playbook integrates the latest patterns and best practices from WWDC 2024 and official Apple documentation to make your tests more powerful, expressive, and maintainable.

---

1. Migration & Tooling Baseline

hboon

Notes

• MCP servers enabled: Brave Search, Fetch, Puppeteer (optional).
• Recommended way to use it: create a project "Deep Research" and add the prompt as custom instructions.
• Recommended model: Sonnet 4 with Thinking. Sonnet vs Opus does not make much difference from experience.
• (As of the time of writing,) Do not enable Claude's built-in web search feature!
  • I've compared the two versions and the quality difference is significant.
  • It seems that the built-in system prompt that gets enabled, is terrible for deep research. A few examples: It explicitly limits Claude to only running one or a few searches in most cases; it contains numerous instructions regarding never quoting directly,

hboon

// Run any SwiftUI view as a Mac app.

import Cocoa
import SwiftUI

NSApplication.shared.run {
    VStack {
        Text("Hello, World")
        	.padding()
            .background(Capsule().fill(Color.blue))

hboon

//
//  GuardURLProtocol.swift
//  URLProtocol
//
//  Created by Bruno Philipe on 16/2/17.
//  Copyright © 2017 Bruno Philipe. All rights reserved.
//
//	Permission is hereby granted, free of charge, to any person obtaining a copy
//	of this software and associated documentation files (the "Software"), to deal
//	in the Software without restriction, including without limitation the rights

hboon

// The trick is to link the DeviceSupport folder from the beta to the stable version.
// sudo needed if you run the Mac App Store version. Always download the dmg instead... you'll thank me later :)

// Xcode 10.2 to Xcode 11 Beta
sudo ln -s /Applications/Xcode-beta.app/Contents/Developer/Platforms/iPhoneOS.platform/DeviceSupport/13.0 /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/DeviceSupport

// Then restart Xcode and reconnect your devices. You will need to do that for every beta of future iOS versions

hboon

import Foundation
import WebKit

final class WebCacheCleaner {
    
    class func clean() {
        HTTPCookieStorage.shared.removeCookies(since: Date.distantPast)
        print("[WebCacheCleaner] All cookies deleted")
        
        WKWebsiteDataStore.default().fetchDataRecords(ofTypes: WKWebsiteDataStore.allWebsiteDataTypes()) { records in

hboon

JavaScriptCore is a built-in iOS library that enables you to use JavaScript in apps alongside Objective-C and Swift. It lets developers read JavaScript from a string, execute it from Objective-C or Swift, and share data structures and functions across languages. We JavaScriptCore to share code between Web and iOS.

Sharing code helped us produce a high-quality, consistent experience across devices while iterating rapidly.

This post is about why we chose to use JavaScriptCore and what we learned. The biggest challenges to using JavaScriptCore in a production app were performance optimization for older devices and getting the build process right. Luckily, these problems have simple solutions that just weren't documented.

Why did we use JavaScriptCore?

A killer feature of one of our apps is search that is optimized for finding guests by name. Our goals included:

hboon

# coding: utf-8
class IAPScene < SKScene
  include ScreenSizes

  attr_accessor :root

  def button_size
    device_screen_width.fdiv(buttons_per_row + 2)
  end

hboon

/**
 * loadJSONP( url, hollaback [, context] ) -> Null
 * - url (String): URL to data resource.
 * - hollaback (Function): Function to call when data is successfully loaded,
 *   it receives one argument: the data.
 * - context (Object): Context to invoke the hollaback function in.
 * 
 * Load external data through a JSONP interface.
 * 
 * ### Examples

hboon

// an example of using CommonCrypto's PBKDF2 function
//
// build with:
//
//   clang -o pbkdf2test pbkdf2test.c
//
// test with:
//
//   ./pbkdf2test <some plaintext password here>