swift-testing-pro

A coding guide for Swift Testing, Apple’s newer framework for writing automated tests in Swift. It helps write and review unit and integration tests, including tests that use asynchronous code.

In plain words
What is it for?
Use it to write, review, improve, or migrate Swift Testing tests in Swift 6.2 or later projects. It covers async tests, networking mocks, test time limits, actor isolation, and newer Swift Testing features.
Why use it?
It helps catch incorrect test structure, assertions, dependency setup, concurrency handling, and outdated APIs. It also guides migrations from XCTest, the older Swift testing framework, while leaving UI tests on XCTest.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/jacklandrin/onlyswitch/swift-testing-pro
Any agent
npx skills add jacklandrin/OnlySwitch --skill swift-testing-pro
Clone the repo
git clone --depth 1 https://github.com/jacklandrin/OnlySwitch

Made for: Claude Code, Codex.

Per session 34 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 959 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00034 $0.00959
Opus 5 $0.00017 $0.00479
Sonnet 5 $0.00007 $0.00192
Haiku 4.5 $0.00003 $0.00096

Measured 3d ago against content hash ad4f1bff44b5, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

swift-testing-pro scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

Copies of this mod

3 near-identical copies found in the catalogue:

doc/skills/swift-testing-pro/SKILL.md · 98 lines

How it starts

The opening of the file, as written. The whole thing — 98 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Write and review Swift Testing code for correctness, modern API usage, and adherence to project conventions. Report only genuine problems - do not nitpick or invent issues.

Review process:

  1. Ensure tests follow core Swift Testing conventions using references/core-rules.md.
  2. Validate test structure, assertions, dependency injection, and other best practices using references/writing-better-tests.md.
  3. Check async tests, confirmations, time limits, actor isolation, and networking mocks using references/async-tests.md.
  4. Ensure new features like raw identifiers, test scopes, exit tests, and attachments are used correctly using references/new-features.md.
  5. If migrating from XCTest, follow the conversion guidance in references/migrating-from-xctest.md.

If doing partial work, load only the relevant reference files.

Core Instructions

  • Target Swift 6.2 or later, using modern Swift concurrency.
  • As a Swift Testing developer, the user wants all new unit and integration tests to be written using Swift Testing, and they may ask for help migrating existing XCTest code to Swift Testing.
  • Swift Testing does not support UI tests – XCTest must be used there.
  • Use a consistent project structure, with folder layout determined by app features.

Swift Testing evolves with each Swift release, so expect three to four releases each year, each introducing new features. This means existing training data you have will naturally be outdated or missing key features.

This skill specifically draws upon the very latest Swift and Swift Testing code, which means it will suggest things you are not aware of. Treat the user’s installed toolchain as authoritative, but there's a fairly high chance Apple's documentation about the APIs will be stale, so treat them carefully.

Output Format

If the user asks for a review, organize findings by file. For each issue:

  1. State the file and relevant line(s).
  2. Name the rule being violated.
  3. Show a brief before/after code fix.

Read the full file on GitHub · 98 lines

Files

What ships with it

8 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 3d ago First seen · 98 lines · 34 tokens per session scan A ad4f1bff44b5

Subscribe to this mod's changes

swift-testing-pro is a skill published in the GitHub repository jacklandrin/OnlySwitch (5,902 stars, last pushed 3d ago), licensed MIT. It adds 34 tokens to every session and 959 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.