TestAssemblySetup set the unhandled-exception mode and a ThreadException
handler from a module initializer. WinForms stores both per thread
(ThreadContext/NativeWindow thread statics), so they applied only to the
runner thread that loaded the assembly, never to the STA threads the
tests run on. There, an exception escaping a window message or a
BeginInvoke/SynchronizationContext callback still opened a modal
ThreadExceptionDialog in an interactive session, or was silently ignored
otherwise; the handler would also have logged and swallowed it.
Replace the fifteen copied RunSta helpers with StaTestThread.Run, which
selects UnhandledExceptionMode.ThrowException on each STA thread before
it creates a window, so the exception propagates to the test body and
fails the test. Each class keeps its own timeout and message; all
threads are now background threads. Remove TestAssemblySetup.
StaTestThreadTests covers a throwing BeginInvoke callback through
StaTestThread (fails with the original exception) and, as a control,
the default mode on a plain STA thread (the exception goes to the
thread's handler and never reaches the test body). Cross-compiled on
Linux; Windows execution is the windows-desktop CI job.
Address Task 3b quality review:
- FormatSize now emits invariant decimal notation so a comma-decimal
locale cannot produce stock text its own invariant parser rejects.
- Validation notices embed a bounded single-line preview instead of the
full cell value.
- Documented GetPlateOptions' all-or-nothing throwing contract.
- STA test helpers run the worker as a background thread with a
diagnostic timeout message; added a de-DE fractional stock round-trip
regression.
aj