Results are sometimes not propagated

[ChristoWolf]

Hi!

Not sure how to really put this, but I have encountered this behavior now a few times.

Sometimes, when setting some result variable in PoseContext.Isolate, the variable's content is not changed.

I have below an example where it happens, but I also haven't figured out yet how to pinpoint the issue.
What happens:

• The shim is executed (breakpoints in it are hit).
• PoseContext.Isolate throws:

   System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.NullReferenceException: Object reference not set to an instance of an object.
    at stub_callvirt_FluentAssertions.Primitives.ObjectAssertions`2[System.Object,FluentAssertions.Primitives.ObjectAssertions]_BeEquivalentTo[Point](ObjectAssertions`2 , Point , String , Object[] )
  --- End of inner exception stack trace ---
      at System.RuntimeMethodHandle.InvokeMethod(Object target, Span`1& arguments, Signature sig, Boolean constructor, Boolean wrapExceptions)
     at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
     at System.Delegate.DynamicInvokeImpl(Object[] args)
     at System.Delegate.DynamicInvoke(Object[] args)
     at Pose.PoseContext.Isolate(Action entryPoint, Shim[] shims)
  

[TestMethod]
[DoNotParallelize]
public void TestGetCenterViaClickablePoint()
{
    var point = new System.Windows.Point(123, 3456);
    var expected = new Point((int)point.X, (int)point.Y);
    var matcher = Is.A<System.Windows.Point>();
    var shim = Shim.Replace(() =>
        Is.A<AutomationElement>().TryGetClickablePoint(out matcher))
        .With((AutomationElement @this, out System.Windows.Point p) =>
        {
            p = point;
            return true;
        });
    Point? actual = null;

    PoseContext.Isolate(() =>
        {
            actual = sut.GetCenter();
            actual.Should().BeEquivalentTo(expected);
        }, shim);
}

with

public static Point GetCenter(this AutomationElement element)
{
    if (!element.TryGetClickablePoint(out var point))
    {
        var rect = element.Current.BoundingRectangle;
        point = new(
            (int)(rect.Left + rect.Width / 2),
            (int)(rect.Top + rect.Height / 2));
    }
    return new Point((int)point.X, (int)point.Y);
}

When the assertion is moved outside of PoseContext.Isolate, then the test host crashes:

The active test run was aborted. Reason: Test host process crashed : Fatal error. Internal CLR error. (0x80131506)
   at System.RuntimeMethodHandle.InvokeMethod(System.Object, System.Span`1<System.Object> ByRef, System.Signature, Boolean, Boolean)
   at System.Reflection.RuntimeMethodInfo.Invoke(System.Object, System.Reflection.BindingFlags, System.Reflection.Binder, System.Object[], System.Globalization.CultureInfo)
   at System.Delegate.DynamicInvokeImpl(System.Object[])
   at System.Delegate.DynamicInvoke(System.Object[])
   at Pose.PoseContext.Isolate(System.Action, Pose.Shim[])
   at <redacted>.TestGetCenterViaClickablePoint()
   at System.RuntimeMethodHandle.InvokeMethod(System.Object, System.Span`1<System.Object> ByRef, System.Signature, Boolean, Boolean)
   at System.Reflection.RuntimeMethodInfo.Invoke(System.Object, System.Reflection.BindingFlags, System.Reflection.Binder, System.Object[], System.Globalization.CultureInfo)
   at System.Reflection.MethodBase.Invoke(System.Object, System.Object[])
   at Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.Extensions.MethodInfoExtensions.InvokeAsSynchronousTask(System.Reflection.MethodInfo, System.Object, System.Object[])
   at Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.Execution.TestMethodInfo+<>c__DisplayClass40_0.<ExecuteInternal>b__0()
   at Microsoft.VisualStudio.TestPlatform.MSTestAdapter.PlatformServices.ThreadOperations.ExecuteWithAbortSafety(System.Action)
   at Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.Execution.TestMethodInfo.ExecuteInternal(System.Object[])
   at Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.Execution.TestMethodInfo.Invoke(System.Object[])
   at Microsoft.VisualStudio.TestTools.UnitTesting.TestMethodAttribute.Execute(Microsoft.VisualStudio.TestTools.UnitTesting.ITestMethod)
   at Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.Execution.TestMethodRunner.ExecuteTest(Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.Execution.TestMethodInfo)
   at Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.Execution.TestMethodRunner.RunTestMethod()
   at Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.Execution.TestMethodRunner.Execute()
   at Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.Execution.UnitTestRunner.RunSingleTest(Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.ObjectModel.TestMethod, System.Collections.Generic.IDictionary`2<System.String,System.Object>)
   at Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.Execution.TestExecutionManager.ExecuteTestsWithTestRunner(System.Collections.Generic.IEnumerable`1<Microsoft.VisualStudio.TestPlatform.ObjectModel.TestCase>, Microsoft.VisualStudio.TestPlatform.ObjectModel.Adapter.IRunContext, Microsoft.VisualStudio.TestPlatform.ObjectModel.Adapter.ITestExecutionRecorder, System.String, System.Collections.Generic.IDictionary`2<System.String,System.Object>, Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.Execution.UnitTestRunner)
   at Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.Execution.TestExecutionManager.ExecuteTestsInSource(System.Collections.Generic.IEnumerable`1<Microsoft.VisualStudio.TestPlatform.ObjectModel.TestCase>, Microsoft.VisualStudio.TestPlatform.ObjectModel.Adapter.IRunContext, Microsoft.VisualStudio.TestPlatform.ObjectModel.Adapter.IFrameworkHandle, System.String, Boolean)
   at Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.Execution.TestExecutionManager.ExecuteTests(System.Collections.Generic.IEnumerable`1<Microsoft.VisualStudio.TestPlatform.ObjectModel.TestCase>, Microsoft.VisualStudio.TestPlatform.ObjectModel.Adapter.IRunContext, Microsoft.VisualStudio.TestPlatform.ObjectModel.Adapter.IFrameworkHandle, Boolean)
   at Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.Execution.TestExecutionManager.RunTests(System.Collections.Generic.IEnumerable`1<Microsoft.VisualStudio.TestPlatform.ObjectModel.TestCase>, Microsoft.VisualStudio.TestPlatform.ObjectModel.Adapter.IRunContext, Microsoft.VisualStudio.TestPlatform.ObjectModel.Adapter.IFrameworkHandle, Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.TestRunCancellationToken)
   at Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.MSTestExecutor.RunTests(System.Collections.Generic.IEnumerable`1<Microsoft.VisualStudio.TestPlatform.ObjectModel.TestCase>, Microsoft.VisualStudio.TestPlatform.ObjectModel.Adapter.IRunContext, Microsoft.VisualStudio.TestPlatform.ObjectModel.Adapter.IFrameworkHandle)
   at Microsoft.VisualStudio.TestPlatform.Common.ExtensionDecorators.SerialTestRunDecorator.RunTests(System.Collections.Generic.IEnumerable`1<Microsoft.VisualStudio.TestPlatform.ObjectModel.TestCase>, Microsoft.VisualStudio.TestPlatform.ObjectModel.Adapter.IRunContext, Microsoft.VisualStudio.TestPlatform.ObjectModel.Adapter.IFrameworkHandle)
   at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Execution.RunTestsWithTests.InvokeExecutor(Microsoft.VisualStudio.TestPlatform.Common.ExtensionFramework.Utilities.LazyExtension`2<Microsoft.VisualStudio.TestPlatform.ObjectModel.Adapter.ITestExecutor,Microsoft.VisualStudio.TestPlatform.Common.Interfaces.ITestExecutorCapabilities>, System.Tuple`2<System.Uri,System.String>, Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Adapter.RunContext, Microsoft.VisualStudio.TestPlatform.ObjectModel.Adapter.IFrameworkHandle)
   at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Execution.BaseRunTests.RunTestInternalWithExecutors(System.Collections.Generic.IEnumerable`1<System.Tuple`2<System.Uri,System.String>>, Int64)
   at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Execution.BaseRunTests.RunTestsInternal()
   at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Execution.BaseRunTests.RunTests()
   at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Execution.ExecutionManager.StartTestRun(System.Collections.Generic.IEnumerable`1<Microsoft.VisualStudio.TestPlatform.ObjectModel.TestCase>, System.String, System.String, Microsoft.VisualStudio.TestPlatform.ObjectModel.Engine.ClientProtocol.TestExecutionContext, Microsoft.VisualStudio.TestPlatform.ObjectModel.Engine.ITestCaseEventsHandler, Microsoft.VisualStudio.TestPlatform.ObjectModel.Client.IInternalTestRunEventsHandler)
   at Microsoft.VisualStudio.TestPlatform.CommunicationUtilities.TestRequestHandler+<>c__DisplayClass45_5.<OnMessageReceived>b__4()
   at Microsoft.VisualStudio.TestPlatform.CommunicationUtilities.TestRequestHandler+<>c.<.ctor>b__31_2(System.Action)
   at Microsoft.VisualStudio.TestPlatform.Utilities.JobQueue`1[[System.__Canon, System.Private.CoreLib, Version=6.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].SafeProcessJob(System.__Canon)
   at Microsoft.VisualStudio.TestPlatform.Utilities.JobQueue`1[[System.__Canon, System.Private.CoreLib, Version=6.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].BackgroundJobProcessor(System.String)
   at Microsoft.VisualStudio.TestPlatform.Utilities.JobQueue`1[[System.__Canon, System.Private.CoreLib, Version=6.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].<.ctor>b__16_0()
   at System.Threading.Tasks.Task.InnerInvoke()
   at System.Threading.Tasks.Task+<>c.<.cctor>b__272_0(System.Object)
   at System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object)
   at System.Threading.Tasks.Task.ExecuteWithThreadLocal(System.Threading.Tasks.Task ByRef, System.Threading.Thread)
   at System.Threading.Tasks.Task.ExecuteEntryUnsafe(System.Threading.Thread)
   at System.Threading.Tasks.ThreadPoolTaskScheduler+<>c.<.cctor>b__10_0(System.Object)
   at System.Threading.Thread.StartCallback()

If I instead execute (notice actual being initialized with Point.Empty, being a value type)

var point = new System.Windows.Point(123, 3456);
var expected = new Point((int)point.X, (int)point.Y);
var matcher = Is.A<System.Windows.Point>();
var shim = Shim.Replace(() =>
    Is.A<AutomationElement>().TryGetClickablePoint(out matcher))
    .With((AutomationElement @this, out System.Windows.Point p) =>
    {
        p = point;
        return true;
    });
var actual = Point.Empty;

PoseContext.Isolate(() =>
    {
        actual = sut.GetCenter();
    }, shim);

actual.Should().BeEquivalentTo(expected);

nothing crashes, but the test fails with

Expected actual to be {X=123,Y=3456}, but found {X=0,Y=0}.

So I guess it might have something to do with the type of the variable to be set, but I have no other idea what's going on.

Any help would be greatly appreciated!

Versions used:

• .NET 8 SDK
• Poser v2.1.0
• MSTest v2.2.10

[Miista]

Hi @ChristoWolf

I have done some investigation and it looks like this is caused by Point being a value type (as you mentioned yourself). When I replicated it locally but "replaced" Point with a type being an object, everything worked as expected.

I will have to look into this.

Could you please try moving the declaration of point into the replacement? Like so:

var shim = Shim.Replace(() =>
    Is.A<AutomationElement>().TryGetClickablePoint(out matcher))
    .With((AutomationElement @this, out System.Windows.Point p) =>
    {
        p = new Point(123, 3456);
        return true;
    });

[ChristoWolf]

Hi @Miista!

Thanks for the quick response!

I tried moving the initialization into the With's lambda, but that did not help.
I also tried making actual an object (at least that is what I gathered from your response too), but that worked neither.

[Miista]

Hi @ChristoWolf

Please try the following implementation for GetCenter:

public static Point GetCenter(this AutomationElement element)
{
    if (!element.TryGetClickablePoint(out var point))
    {
        var rect = element.Current.BoundingRectangle;
        point = new(
            (int)(rect.Left + rect.Width / 2),
            (int)(rect.Top + rect.Height / 2));
    }
    var center = new Point((int)point.X, (int)point.Y);

    return center;
}

For reasons unknown it seems that having the center variable there causes the value to be returned.

[ChristoWolf]

Haven't tried it yet, but that's interesting behavior.

According to the internet, they should actually compile to the same code (haven't checked myself yet).

Could this have anything to do with boxing?