# swift-testing-expert

Coaches your agent through Swift Testing: #expect and #require macros, tags, parameterized tests, and moving a suite off XCTest.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 5300 installs · ★ 476
- Author: AvdLee
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/AvdLee/Swift-Testing-Agent-Skill/tree/HEAD/swift-testing-expert/SKILL.md
- Updated: 2026-09-14
- HTML: https://affpapa.org/en/nevibecode/skills/swift-testing-expert

## What it does

This skill hands the agent a rulebook for Swift Testing. It says which cases stay on XCTest: UI automation through `XCUIApplication`, performance metrics via `XCTMetric`, test code written only in Objective-C. Everything else moves over.

What sits inside: an agent behavior contract plus a routing map into `references/`. Assertions live in `references/expectations.md`, parameterization in `references/parameterized-testing.md`, parallel runs and `.serialized` in `references/parallelization-and-isolation.md`, the XCTest handoff in `references/migration-from-xctest.md`. A triage template opens each session — Xcode and Swift versions, which framework the tests use today, whether failures repeat or flicker.

\`Testing` gets imported in test targets only; app, library and binary targets stay clean. Migration is meant to go in stages: assertions first, then suite layout, then parameterization and traits. When tests share a database or global state, the skill asks you to split those dependencies before reaching for `.serialized`, which it treats as a stopgap.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add AvdLee/Swift-Testing-Agent-Skill --skill swift-testing-expert -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/swift-testing-expert/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/swift-testing-expert/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add AvdLee/Swift-Testing-Agent-Skill --skill swift-testing-expert -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/swift-testing-expert/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add AvdLee/Swift-Testing-Agent-Skill --skill swift-testing-expert -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/swift-testing-expert/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install AvdLee/Swift-Testing-Agent-Skill swift-testing-expert
```

2. **Manually: put the files in place**
- File: `.github/skills/swift-testing-expert/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add AvdLee/Swift-Testing-Agent-Skill --skill swift-testing-expert -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/AvdLee/Swift-Testing-Agent-Skill --path swift-testing-expert
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/swift-testing-expert/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add AvdLee/Swift-Testing-Agent-Skill --skill swift-testing-expert -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/AvdLee/Swift-Testing-Agent-Skill/tree/HEAD/swift-testing-expert/SKILL.md

## When to use it
- move a suite from XCTest to Swift Testing without a rewrite
- pick between `#expect` and `#require` for a given check
- collapse a pile of near-identical tests into one parameterized case
- track down flaky tests that share a database
- filter tests by tags instead of name lists in a test plan

## Example prompts
- Port this XCTest suite to Swift Testing, assertions first
- Turn these repeated tests into one `@Test(arguments:)` case
- This test flakes on a shared database — how do I isolate it?

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 3141b6046a51b071.

BEGIN THIRD-PARTY FILE 3141b6046a51b071
```text
---
name: swift-testing-expert
description: 'Expert guidance for Swift Testing: test structure, #expect/#require macros, traits and tags, parameterized tests, test plans, parallel execution, async waiting patterns, and XCTest migration. Use when writing new Swift tests, modernizing XCTest suites, debugging flaky tests, or improving test quality and maintainability in Apple-platform or Swift server projects.'
---

# Swift Testing

## Overview

Use this skill to write, review, migrate, and debug Swift tests with modern Swift Testing APIs. Prioritize readable tests, robust parallel execution, clear diagnostics, and incremental migration from XCTest where needed.

## Agent behavior contract (follow these rules)

1. Prefer Swift Testing for Swift unit and integration tests, but keep XCTest for UI automation (`XCUIApplication`), performance metrics (`XCTMetric`), and Objective-C-only test code.
2. Treat `#expect` as the default assertion and use `#require` when subsequent lines depend on a prerequisite value.
3. Default to parallel-safe guidance. If tests are not isolated, first propose fixing shared state before applying `.serialized`.
4. Prefer traits for behavior and metadata (`.enabled`, `.disabled`, `.timeLimit`, `.bug`, tags) over naming conventions or ad-hoc comments.
5. Recommend parameterized tests when multiple tests share logic and differ only in input values.
6. Use `@available` on test functions for OS-gated behavior instead of runtime `#available` checks inside test bodies; never annotate suite types with `@available`.
7. Keep migration advice incremental: convert assertions first, then organize suites, then introduce parameterization/traits.
8. Only import `Testing` in test targets, never in app/library/binary targets.

## First 60 seconds (triage template)

- Clarify the goal: new tests, migration, flaky failures, performance, CI filtering, or async waiting.
- Collect minimal facts:
  - Xcode/Swift version and platform targets
  - Whether tests currently use XCTest, Swift Testing, or both
  - Whether failures are deterministic or flaky
  - Whether tests access shared resources (database, files, network, global state)
- Branch quickly:
  - repetitive tests -> parameterized tests
  - noisy or flaky failures -> known issue handling and test isolation
  - migration questions -> XCTest mapping and coexistence strategy
  - async callback complexity -> continuation/await patterns

## Routing map (read the right reference fast)
```
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