Refactor: qfcformcontroller-actions-testability-seams

[drmoisan]

• Work Mode: minor-audit

Problem / Why

QuickFiler/Controllers/QfcFormController.Actions.cs sits at 47.89% line and 45.24% branch coverage because three blocks of it cannot be exercised without injectable seams. Measured during issue #446, the uncovered set is:

Lines	Block	Why untestable today
29-160	LoadItems / LoadItemsAsync overloads	bound directly to TableLayoutPanel and Outlook COM types with no seam
241-258	ProcessUndoItemAsync	COM-and-dispatcher take branch
267-306	UndoDialog	three modal MessageBox.Show calls at :225, :238 and :248

This was accepted as a documented carve-out for #446 because the Bugfix Workflow requires a minimal targeted fix and directs that deeper design problems be opened as a new issue rather than widening scope. The #446 feature review confirmed the carve-out was legitimate but recorded that no promoted document routed the resulting debt, which is what this entry fixes.

One correction to the original #446 rationale, established by the review: the carve-out note named only the MessageBox.Show calls, which understates the problem. A MessageBox seam alone would lift the file to roughly 67%, not past 90%, because the COM-bound loader overloads at 29-160 dominate the uncovered set. Any plan that seams only the dialog will miss the target.

Implementation Intent

Introduce injectable seams so the three blocks become testable without a live Outlook or a real WinForms message pump:

• a dialog-service seam replacing direct MessageBox.Show calls;
• loader seams isolating TableLayoutPanel and COM interaction from the LoadItems* control flow;
• a seam or fake for the ProcessUndoItemAsync take branch's COM and dispatcher dependencies.

Pure logic moves behind the seams and is covered by unit tests; the residual host-bound wiring stays as thin as possible.

Acceptance Criteria

• QuickFiler/Controllers/QfcFormController.Actions.cs line coverage is at least 90%
• Branch coverage on that file is at least 75%
• No [ExcludeFromCodeCoverage] is added to reach the target
• No test starts a real dialog, message pump, or live COM object
• Existing behavior is unchanged and the full QuickFiler.Test assembly remains green

Dependencies / Risks

• The repository's policy direction disfavors coverage exemptions where the real answer is a testability seam, so [ExcludeFromCodeCoverage] is not an acceptable route here.
• QfcFormController is a partial type; sibling declarations are owned by other epic children (features 442, 484, 444, 489). Coordinate to avoid annexing their scope.
• The file is currently 496 of the 500-line cap, so seam work must extract rather than add.
• UT4 prohibits exercising modal dialogs and live COM in unit tests; the seams exist precisely to keep tests off them.

Verification Steps

• Dialog seam: each of the three call sites drives its branch through an inert fake
• Loader seams: positive, empty, and error paths for both LoadItems* overloads
• ProcessUndoItemAsync: take branch, exception branch, and cancellation
• Coverage re-measured on the changed-file scope, with the denominator stated

Evidence Checklist

• Baseline
• End-state
• Targeted verification

Source

From: docs/features/potential/2026-08-26-qfcformcontroller-actions-testability-seams.md