Swift Testing

What it does

When your agent uses it

• Writing new tests
• Converting existing Quick+Nimble specs to Swift Testing
• Reviewing test quality
• Debugging flaky tests

Example prompts

• “write test”
• “add test”
• “test this”
• “/swift-testing”

Workflow steps

9 steps, taken from the first numbered list in SKILL.md.

1. 1Swift Testing for all new unit/integration tests. Retain Quick+Nimble only for existing specs; do not migrate unless asked.
2. 2Use #expect as the default assertion; use #require only when subsequent lines depend on a prerequisite value.
3. 3Design tests to run safely in parallel by default. Fix shared state before reaching for .serialized.
4. 4Use inline private struct / private actor stubs conforming to domain protocols — no generated mocks.
5. 5Use actor stubs when the protocol requires async or has mutable state; use struct stubs otherwise.
6. 6Prefer parameterized tests (@Test(arguments:)) over duplicated test methods.
7. 7Use traits (.enabled, .disabled, .timeLimit, .bug, .tags) instead of ad-hoc comments.
8. 8Import Testing only in test targets, never in app/library targets.
9. 9Keep tests deterministic — no real network calls. Use NetworkStubber (OHHTTPStubs) for network-level tests.

What it can do on your machine

Read from SKILL.md and the folder at commit f009d02. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  No scripts in the folder and no shell commands in SKILL.md (its code samples are swift).

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  No URLs in SKILL.md.

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Swift Testing loads about 1.3k tokens when it runs, and up to ~6.8k if it reads all its reference files. Until then it costs about 99 tokens; SKILL.md has 429 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~99

When it runs · the whole SKILL.md, loaded when a task matches

~1.3k

With references · SKILL.md plus every file in references/, read only if the agent opens them

~6.8k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from nimblehq/ios-templates at commit f009d02, republished under its MIT licence (© nimblehq). 429 words, ~1,258 tokens.

name

swift-testing

description

Write, review, or migrate unit tests using Swift Testing (@Test, @Suite, #expect, #require). Use when writing new tests, converting existing Quick+Nimble specs to Swift Testing, reviewing test quality, debugging flaky tests, or improving test structure in this iOS template project. Triggers on: "write test", "add test", "test this", "migrate test", "convert spec", "Swift Testing".

import Testing

@testable import Data
import Domain

@Suite("DefaultRemoteConfigRepository")
struct DefaultRemoteConfigRepositoryTests {

    @Test("returns a typed stored value")
    func returnsATypedStoredValue() async {
        let booleanKey = RemoteConfigKey(name: "feature_enabled", defaultValue: false)
        let repository = DefaultRemoteConfigRepository(
            source: StubRemoteConfigSource(values: [
                booleanKey.name: .string("true")
            ])
        )

        let value = await repository.value(for: booleanKey)

        #expect(value == true)
    }
}

private actor StubRemoteConfigSource: RemoteConfigSource {

    private let values: [String: RemoteConfigStoredValue]

    init(values: [String: RemoteConfigStoredValue] = [:]) {
        self.values = values
    }

    func refresh() async throws {}

    func value(forKey key: String) async -> RemoteConfigStoredValue? {
        values[key]
    }
}

© nimblehq, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 6 other files (references) in skills/swift-testing of nimblehq/ios-templates.

• SKILL.md
• references/async-testing.md
• references/expectations.md
• references/fundamentals.md
• references/parameterized-testing.md
• references/test-doubles.md
• references/traits-and-tags.md

Open the folder on GitHubat commit f009d02