Description

ProcessTests.Start_Disposed_ThrowsObjectDisposedException fails deterministically on all Apple mobile platforms (iOS, tvOS, MacCatalyst) across both CoreCLR and Mono.

Error

Assert.Throws() Failure: Exception type was not an exact match
Expected: typeof(System.ObjectDisposedException)
Actual:   typeof(System.PlatformNotSupportedException)
---- System.PlatformNotSupportedException : Operation is not supported on this platform.
   at System.Diagnostics.Process.Start()

Root Cause

Process.Start() on iOS/tvOS/MacCatalyst throws PlatformNotSupportedException (process launching is unsupported) before checking disposal state. The test expects ObjectDisposedException which never fires.

Impact

Fails in 7 legs of runtime-extra-platforms rolling builds (iossimulator-x64/arm64, tvos-arm64 across CoreCLR, Mono, and Debug), contributing to 100% rolling build failure rate.

Proposed Fix

Add [SkipOnPlatform(TestPlatforms.iOS | TestPlatforms.tvOS | TestPlatforms.MacCatalyst, "Process.Start() is not supported on iOS, tvOS, and MacCatalyst.")] — consistent with the pattern used by 20+ other tests in the same file.

Build Reference

Build 1369438 — runtime-extra-platforms rolling, main branch, 2026-04-08.

Related: #126455 (covered ProcessHandlesTests but not this test)