test: comprehensive unit tests for single-pane layout strategies

[sandy081]

Summary

Adds singlePaneStrategies.test.ts — focused unit tests for each composed single-pane layout strategy in isolation, complementing the existing controller-level integration tests in desktopSessionLayoutController.test.ts.

The single-pane layout (shipped in #324657) is composed from eight strategy objects under contrib/layout/browser/singlePane/. These tests instantiate each real strategy class directly via createInstance(StrategyClass, ctx, ...) — driving the actual constructor autoruns, event listeners, and private sync logic — with the shared createTestHarness service doubles and a hand-built ISinglePaneLayoutContext (createStrategyTestContext) that exposes the coordination flags (isRestoringSessionLayout, togglingSidePane, hidingAuxiliaryBarForRestore) and the viewStateBySession map the controller normally owns.

Coverage (46 tests)

Strategy	Tests	Notable edges
NewSessionRulesStrategy (R1)	6	become-visible hide, inherited-visible hide on entry, explicit-reveal respected, created/quick-chat/multi-visible excluded
QuickChatEditorHideStrategy	4	hide only when empty group; not for real editor / non-quick-chat / already-hidden
DetailVisibilityStrategy (D1-D4)	13	switch-away capture, live D2 capture + guards, D3b default reveal/hide, D3c leave-as-is with no saved state, intrinsic submit reveal Changes vs hidden, collapse marker
DetailPanelStrategy	9	quick-chat/empty to Hidden, empty-group to Preserve during restore, Changes/Files mapping, forced targets, no-reveal when hidden, maximized to Changes
ManagedTabsStrategy	6	ensure Changes+Files, uncreated files-only, quick-chat none, dismissal memory + + Files context, reopen clears dismissal, workspace-file collapse
EditorAreaCollapseStrategy	4	collapse/restore non-managed, skip during restore, skip managed placeholder
ResponsiveSidebarStrategy (D7)	4	toggleDetails open+auto-hide / close+restore, restore on full side-pane hide, manual toggle hands back

Validation

• typecheck-client, transpile: clean
• 46 (new) + 114 (controller) + 45 (workbench) tests pass, no disposable leaks
• valid-layers-check, eslint: clean

Test-only change; no production code modified.

Co-authored-by: Copilot 223556219+Copilot@users.noreply.github.com

[vs-code-engineering]

📬 CODENOTIFY

The following users are being notified based on files changed in this PR:

@benibenj

Matched files:

• src/vs/sessions/contrib/layout/test/browser/singlePaneStrategies.test.ts

[Copilot]

Pull request overview

This is a test-only PR that adds singlePaneStrategies.test.ts, providing focused unit coverage for each of the eight composed single-pane layout strategy objects introduced in #324657 (contrib/layout/browser/singlePane/). Rather than exercising behavior only through the controller integration tests, each real strategy class is instantiated in isolation via createInstance(StrategyClass, ctx, …) against the shared createTestHarness service doubles and a hand-built ISinglePaneLayoutContext (createStrategyTestContext) that exposes the coordination flags (isRestoringSessionLayout, togglingSidePane, hidingAuxiliaryBarForRestore) and viewStateBySession map the controller normally owns. A companion note is added to the sessions SKILL doc describing this per-strategy testing approach and its two gotchas.

Changes:

• Adds 46 unit tests across the seven single-pane strategies (new-session rules, quick-chat editor hide, detail visibility, detail panel, managed tabs, editor-area collapse, responsive sidebar), including bug-prone edges (D3c leave-as-is, intrinsic submit detection, empty-group→Preserve during restore).
• Introduces createStrategyTestContext, a lightweight ISinglePaneLayoutContext double with mutable coordination flags plus a settle() sequencer-flush helper.
• Documents the isolated per-strategy testing pattern in .github/skills/sessions/SKILL.md.

Show a summary per file

File	Description
src/vs/sessions/contrib/layout/test/browser/singlePaneStrategies.test.ts	New 837-line test suite instantiating each single-pane strategy directly and asserting its isolated behavior; verified to align with each strategy's implementation and to reuse the existing harness/disposable conventions.
.github/skills/sessions/SKILL.md	Adds an accurate learnings bullet describing how to unit-test single-pane strategies in isolation, including the direct-construction of SinglePaneDockedTabsCoordinator and the sequencer settle() caveat.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 1
• Review effort level: Medium