Tim Kersey tkersey

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

MCP's client-server architecture: Technical design for AI integration

The Model Context Protocol (MCP) represents a fundamental shift in how AI applications connect to external systems. Introduced by Anthropic in November 2024, MCP chose a client-server architecture over alternatives like peer-to-peer or monolithic designs to solve the "M×N problem" - where M AI applications need to integrate with N data sources, traditionally requiring M×N custom integrations. The client-server model transforms this into an M+N solution through standardized, secure, and scalable connections.

This architectural decision reflects deep technical considerations: security isolation between components, modular extensibility for diverse integrations, and protocol standardization that enables any MCP client to work with any MCP server regardless of implementation language or platform. The design philosophy prioritizes developer simplicity while maintaining enterprise-grade security boundaries - what Anthropic calls "

What is your setup?

Just chat.deepseek.com with prompts adapted from this gist.

Does it work in one-shot or I have to prompt it multiple times?

For the qX_0 variants, they are actually quite straight-forward so deepseek can come up with a correct result in 1 shot.
For the qX_K it's more complicated, I would say most of the time I need to re-prompt it 4 to 8 more times.
The most difficult was q6_K, the code never works until I ask it to only optimize one specific part, while leaving the rest intact (so it does not mess up everything)

Why did you do this?

Relax, I only have one Sunday to work on idea, literally my weekend project. So I tried Deepseek to see if it can help. Surprisingly, it works and it saves me another weekend...

What is your setup?

Just chat.deepseek.com (cost = free) with prompts adapted from this gist.

Does it work in one-shot or I have to prompt it multiple times?

Recently we’ve noticed a number of our clients maintain a backlog of small tasks that are handled separately from their main backlog. These are tasks that should be finished at some point, but will rarely take priority over business-critical features and bugfixes. Often they are bite-sized pieces of work that can be finished in a couple of hours or less: addressing engineering chores, paying off tech debt, and addressing minor bugs. Internally, this separate backlog has earned a catchy name: the snacklog.

When is it appropriate to work on a snacklog task instead of something in the prioritized backlog? After all, developers should be working on things that move the business forward (obviously). Inevitably, though, natural lulls come up in the course of development:

I’ve just finished a big pull request and have some time before my team finishes leaving feedback.
I’m temporarily blocked by a design or product decision.
It’s near the end of the day, and I’d rather work on something small than sta

	import {
	Operation,
	Resource,
	Context,
	action,
	resource,
	spawn,
	sleep,
	main,
	suspend as effectionSuspend,

	// Deep Dive: Prompts as Delimited Continuations in TypeScript

	// =============================================================================
	// 1. PROMPTS AS INITIAL CONTINUATIONS
	// =============================================================================

	/**
	* Prompts as Initial Continuations treats the prompt itself as the starting
	* continuation that establishes the computational context. The prompt becomes
	* a first-class continuation that can be captured, modified, and resumed.

	import Foundation
	import SwiftUI

	extension View {
	/// Adds introspection to find the parent view controller in the view hierarchy and
	/// makes that view controller available to downstream views in the view hierarchy.
	public func addParentViewControllerIntrospection() -> some View {
	modifier(ParentViewControllerEnvironmentModifier())
	}
	}

	import Testing
	import Combine

	// From https://stackoverflow.com/questions/78892734/getting-task-isolated-value-of-type-async-passed-as-a-strongly-trans/78899940#78899940
	public final class AsyncFuture<Output, Failure: Error>: Publisher, Sendable {
	public typealias Promise = @Sendable (Result<Output, Failure>) -> Void

	private let work: @Sendable (@escaping Promise) async -> Void

	public init(_ work: @Sendable @escaping (@escaping Promise) async -> Void) {

	import Observation

	public protocol _Observable: Observable {
	nonisolated
	func _access<Member>(keyPath: KeyPath<Self, Member>)

	nonisolated
	func _withMutation<Member, MutationResult>(
	keyPath: KeyPath<Self, Member>,
	_ mutation: () throws -> MutationResult