[esnunes]

Review item 20. Each change below was checked against the code or a run before writing it.

Serializing runs

The README suggested .serialized on suites. It isn't enough: .serialized orders only the tests of its own suite and nested suites, and Swift Testing still runs other suites in parallel. Two .serialized suites whose tests wait on each other through gates ran at the same time, and both records came out overlapped.

The README now says to turn off parallel testing for the run, and the Usage example drops .serialized. With either flag, the Fixtures/Concurrency gated tests run one at a time and both records are clean:

• swift test --no-parallel
• xcodebuild test -parallel-testing-enabled NO

The trait's doc comment says the same.

Other changes

• Examples use a fresh directory from mktemp -d instead of a fixed /tmp/attribution (review item 16). The path is kept in a variable and listed afterwards, and parallel testing is off in both commands. I ran the swift test one as written against Fixtures/Example: it records into one directory per test process.
• Guarantees:
  • The coverage-report guarantee names SwiftPM as well as Xcode. test: cover the iOS simulator, static archives and the coverage report #15 tests the SwiftPM report byte for byte, and an xccov comparison showed Xcode's report unchanged.
  • When two copies of the package load, the Objective-C runtime logs a harmless duplicate-class warning (from review item 15).
• Record layout: records are in the host's byte order, little-endian on every Apple platform.
• A new Limitations section:
  • XCTest and Swift Testing run one after the other. Xcode runs a process's XCTest tests before its Swift Testing tests (observed with Xcode 26.3), SwiftPM uses separate processes, and attribution relies on it (from review item 12).
  • UI tests record nothing about the app, whose code runs in a process that doesn't link the package.
  • Images loaded late aren't observed. This moved from Guarantees, since it's a limitation.
  • The package's own code shows up in the records. Under xcodebuild the observer is instrumented, and the trait is instrumented everywhere.

Not changed: the install line stays on branch: "main" until there's a release tag (review items 22–23).

mise run lint passes.

Code review

Fixed:

• Inlined $(mktemp -d). It lost the output path, so readers couldn't find their records.
• .serialized in the Usage example. It contradicted the new text.
• Xcode version. This description named Xcode 26.1 for the XCTest-before-Swift-Testing ordering; it was observed with 26.3.

Not changed:

• "Two test bundles loaded by the same host" as the two-copies example can't be confirmed here.
• The overlap sentence reads as applying to XCTest too, but Limitations already says the two frameworks aren't checked against each other.

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