public void CompletionHandlerIsInvoked()
{
var result = Substitute.For <IDebugProperty2>();
_taskExecutor.SubmitAsync(Arg.Any <Func <Task <EvaluationResult> > >(),
Arg.Any <CancellationToken>(), Arg.Any <string>(),
Arg.Any <Type>())
.Returns(Task.FromResult(EvaluationResult.FromResult(result)));
_evaluateOp.BeginExecute();
_completionHandler
.Received(1)
.OnComplete(VSConstants.S_OK, result);
}