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.

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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

--Modified from https://stackoverflow.com/a/5519588
function diffLineWithNext()
    local f1 = vim.fn.tempname()
    local f2 = vim.fn.tempname()

    vim.api.nvim_command(".w " .. f1)
    vim.api.nvim_command("+1 w " .. f2)

    vim.api.nvim_command("tabedit " .. f1)
    vim.api.nvim_command("hor diffsplit " .. f2)

hboon

#Use this to do `gco -b <branch> <commit>`
function pr
    set --local hash (gcommit)
    #echo "in our pr: $hash"
    set --local msg (git show -s --format=%B $hash | head -1)
    #echo "in our pr: $msg"
    set --local branch (string lower $msg | string replace -a -r "[ /#]" "-" | string replace -a -r "[\(\)\.\[\]'`\":]" "")
    #echo "in our pr: $branch"
    echo "Running: git checkout -b $branch $hash"
    git checkout -b $branch $hash

hboon

#!/usr/bin/env ruby

#Opens URLs embedded in STDIN (so it's useful in vim by selecting text and running it)

require 'uri'

input = $stdin.read.split("\n")

urls = input.map do |line|
  URI.extract(line, ['http', 'https'])

hboon

//Proper way to implement error types. Implement `errorDescription`, not `localizedDescription` and the global handler `getErrorMessage(error: Error)` is easy to implement, not need a stupid switch case
//Key is implement `errorDescription` instead of `localizedDescription` and must not implement `localizedDescription` at all

import Foundation

struct E1: LocalizedError {
    var errorDescription: String? {
      return "E1's errorDescription"
    }
}

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

#!/bin/sh

if git rev-parse --verify HEAD >/dev/null 2>&1; then  
  against=HEAD
else  
  # Initial commit: diff against an empty tree object
  against=4b825dc642cb6eb9a060e54bf8d69288fbee4904
fi

exec 1>&2

hboon

Found a bug in my code because of something very subtle:

class C: NSObject {
	var foo: String = {
		NSLog("non-lazy self: \(self)")
		return ""
	}()
	lazy var bar: String = {
 NSLog("lazy self: \(self)")