Flaky test: SkillLibraryViewTests scroller-style expectation depends on suite order #29

Flaky test

SkillLibraryViewTests.rendersLibraryAtSupportedWidthsWithoutLiveData() (Tests/ContextDaddyTests/SkillLibraryViewTests.swift:119):

Expectation failed: NSScroller.preferredScrollerStyle == (scrollbarPreference == "Always" ? .legacy : .overlay)

This is the one-off failure seen on main at c6bd95b that passed on rerun.

Evidence (local Mac, 2026-10-09, swift test --skip DesignSnapshotTests, same command as CI)

• Full suite: failed 5 of 5 runs, always this single expectation (154 tests otherwise pass).
• swift test --filter rendersLibraryAtSupportedWidthsWithoutLiveData: passed 3 of 3.
• Skipping PluginCountQualificationTests, IssueOneAcceptanceTests and UsageAllowanceViewTests: passed.
• --no-parallel still failed, so this is not only a race.

Cause

The test's own comment says AppKit caches the scroller style per process. The test sets AppleShowScrollBars and then asserts the style, but any suite that builds an NSHostingView or NSScrollView first (those three suites) fixes the style, so the assertion depends on which suite runs first and on the machine's pointing-device default. A clean CI runner mostly lands on legacy, so it usually passes.

Suggested fix (not applied, since it is a test-design decision)

Set AppleShowScrollBars before any AppKit view is created in the process, for example from a shared test bootstrap, or drop the process-global assertion and verify the layout against the style actually in effect. The environment variable CONTEXTDADDY_TEST_SCROLLBARS already exists for per-style runs.