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.
npx skills add markdavidgan/apple-dev-skills --skill regression-testgit clone --depth 1 https://github.com/markdavidgan/apple-dev-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/markdavidgan/apple-dev-skills/regression-test)<a href="https://agentmods.dev/skills/markdavidgan/apple-dev-skills/regression-test"><img src="https://agentmods.dev/badge/skills/markdavidgan/apple-dev-skills/regression-test/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/markdavidgan/apple-dev-skills/regression-test"><img src="https://agentmods.dev/badge/skills/markdavidgan/apple-dev-skills/regression-test.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00110 | $0.01515 |
| Opus 5.5 | $0.00044 | $0.00606 |
| Sonnet 5.5 | $0.00022 | $0.00303 |
| Haiku 4.5 | $0.00011 | $0.00152 |
Grade A, and why
regression-test 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 1mo 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.
How it starts
The opening of the file, as written. The whole thing — 214 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Regression Test Skill
When fixing an iOS/Swift bug, always follow this workflow to prevent the bug from recurring. This assumes you're already using a test-first loop (e.g. superpowers:test-driven-development); the value this skill adds is Step 0 — classifying the bug into an Apple-specific root-cause class and sweeping for siblings — not the write-test/fix/verify loop itself.
Regression Test Workflow
Step 0: Identify the Bug Class
Before writing any test, classify the bug. This determines what else to check.
| Bug Class | Root Cause | Also Search For |
|---|---|---|
Force unwrap crash (!) |
Assumed non-nil, was nil | Other ! in same file/service |
| try! crash | Error ignored at call site | Other try! in same target |
| fatalError crash | Defensive code hit in prod | Other fatalError in prod paths |
| Missing confirmation | Destructive action unguarded | Other destructive actions without .destructive role |
| MainActor isolation crash | Async code off main thread | Other @MainActor + async patterns in same ViewModel |
| App Group mismatch | Entitlements out of sync | All targets sharing the group |
| State not restored | Background/foreground not handled | Other lifecycle observers |
After identifying the class, fix all instances of the class in this file/service — not just the one that crashed. One bug usually means there are siblings.
Step 1: Write Failing Test First
Before fixing the bug, reproduce it in a test that fails:
func test_timer_backgrounding_shouldPause() {
// Given: Running timer
let viewModel = TimerViewModel()
viewModel.start()
// When: App backgrounds
NotificationCenter.default.post(name: UIApplication.didEnterBackgroundNotification, object: nil)
// Then: Timer should be paused
XCTAssertEqual(viewModel.state, .paused)
}
Why first? Ensures you understand the bug and can prove the fix works.
Step 2: Fix the Bug
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.
- 1mo ago First seen · 214 lines · 110 tokens per session scan A fea2613092df
regression-test is a skill published in the GitHub repository markdavidgan/apple-dev-skills (5 stars, last pushed 1mo ago), licensed MIT. It adds 110 tokens to every session and 1,515 once invoked, about $0.0004 per session on Opus 5.5. 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 2026-09-03.
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Fixes an observed defect with reproducible evidence in one call: writes a short trace doc before touching code, implements the fix, and backs it with a regression test written before the fix. Production incidents are the motivating case, not a gate. When blocked, it halts by name and saves the doc for a later call to…
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