macOS Test Diagnoser

Quick Start

Use this skill to run the smallest meaningful test scope first, classify failures precisely, and avoid treating every test failure like a product bug.

Workflow

1. Detect the test harness.

• Use xcodebuild test for Xcode-based projects.
• Use swift test for SwiftPM packages.

1. Narrow the scope.

• If the user gave a target, product, or test filter, use it.
• If not, prefer the smallest likely failing target before a full suite.

1. Classify the result.

• Build failure
• Assertion failure
• Crash or signal
• Async timing or flake
• Environment or fixture setup issue
• Missing entitlement or host app issue

1. Rerun intelligently.

• Use focused reruns when a specific case fails.
• Avoid burning time on full-suite reruns without new information.

1. Summarize clearly.

• What command ran
• Which tests failed
• What kind of failure it was
• The best next proof step or fix path

Guardrails

• Distinguish compilation failures from test execution failures.
• Call out when a test appears to assume iOS-only or simulator-only behavior.
• Mark likely flakes as such instead of overstating confidence.

Output Expectations

Provide:

• the command used
• the smallest failing scope
• the top failure category
• a concise explanation of the likely cause
• the next rerun or fix step