Test Studio 2017.1 / System.InvalidOperationException: Collection was modified

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Test Execution WPF Testing
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Andonié asked on 30 Apr 2021, 08:21 AM


We bought few years ago the Tekerik Test Studio 2017.1.207.0.

When we run tests, and application windows or popup are closed, we frequently have the message :

Failure Information:
Collection was modified; enumeration operation may not execute.
System.InvalidOperationException: Collection was modified; enumeration operation may not execute.
   at System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource)
   at System.Collections.Generic.List`1.Enumerator.MoveNextRare()
   at System.Collections.Generic.List`1.Enumerator.MoveNext()
   at System.Linq.Enumerable.LastOrDefault[TSource](IEnumerable`1 source, Func`2 predicate)
   at ArtOfTest.WebAii.Core.Manager.get_ActiveWpfWindow()
   at ArtOfTest.WebAii.Design.Execution.ExecutionEngine.ExecuteStep(Int32 order)

We tried to add a wait command after the close but it does not succeeded.

Is there a workaround to bypass this bug ?

Is this bug fixed in latest version ?

Thanks in advance,

Best regards.

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Telerik team
answered on 04 May 2021, 12:02 PM

Hello Alexandre,

Test Studio team constantly works on improving the product features and stability. There are plenty of issues fixed in the past few years since you bought Test Studio including such related to WPF applications. 

I searched your account and also our database for similar issue reported and so far I couldn't find any thread on this particular topic. Have you contacted us to investigate this issue back then when you have first encountered the misbehavior? 

We need to consider that WPF errors are often specific for the particular application and how it is built. That said, we need to investigate that specific WPF app and its behavior to evaluate what causes the exceptions and find a fix for these. 

On the other hand, Test Studio is constantly evolving and in the latest versions you may not encounter these errors on closing popups and windows anymore. As far as I can recall you had recently activated a trial for the latest version of Test Studio - did you have the chance to explore it? Did you face the same failures for the specific tests? 

Do you find it possible to install the latest version of Test Studio and give it a try?

I know you had troubles with re-activating your old license, which was caused by a change on our end, and although this was fixed, you can install the latest Test Studio on another machine - to keep your own without issues. Then move a copy of the test project and run it against the application under test. Then, if the same issue appears again, we can investigate it.

An alternative for this could be the following - provide us the application under test and the test project and point us to the specific tests or test lists, which reproduces the error. If this is still there, we will be working on resolving it. 

Please, do not hesitate to get back to me with any doubts or further questions you might have.

Thank you for your cooperation in advance.

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