Writing Unit Tests for WinForms Control APIs

These rules apply when writing unit tests for new public properties, methods, events, and virtual methods on WinForms controls or components. For the API implementation itself, see the new-control-api skill.

Golden rule: Every new public API member needs tests that verify default values, get/set round-trips, event firing, event idempotency, and behavior both with and without a native window handle.

1. Test Project Structure

1.1 Test location

Control tests live under: