Unstable unit test: System.Windows.Forms.Tests.TextBoxBaseTests.TextBoxBase_ClearUndo_CanUndo_Success

[LeafShi1]

Related #11227

Test

System.Windows.Forms.Tests.TextBoxBaseTests.TextBoxBase_ClearUndo_CanUndo_Success

Issue description

The case failed in PR build, the pipeline link:

• https://dev.azure.com/dnceng-public/public/_build?definitionId=76&_a=summary

Error Message:

• In X86 unit:

  • Assert.Equal() Failure: Strings differ ↓ (pos 0) Expected: "bcxt" Actual: "xt" ↑ (pos 0)

Stack trace:

   at System.Windows.Forms.Tests.TextBoxBaseTests.TextBoxBase_ClearUndo_CanUndo_Success() in /_/src/System.Windows.Forms/tests/UnitTests/TextBoxBaseTests.cs:line 4148
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Void** arguments, Signature sig, Boolean isConstructor)
   at System.Reflection.MethodBaseInvoker.InterpretedInvoke_Method(Object obj, IntPtr* args)
   at System.Reflection.MethodBaseInvoker.InvokeWithNoArgs(Object obj, BindingFlags invokeAttr)