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NUnit STA Threads & Testing WPF

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17 Jun 2009CPOL1 min read 35K   209   3   4
NUnit STA threads and testing WPF

During the course of the WPF project we are working on at work, we decided to go down the Agile/XP/TDD/Mocks/Continuous Integration route, which means Unit tests, lots of them.

We are using NUnit, which I really like, but we are also using WPF, we are obviously using the latest/greatest patterns AKA MVVM, but from time to time, it is nice to be able to test certain things on WPF controls/windows, etc.

So I set out to create a small NUnit test like the following:


Now to me this looked fine, but when I ran this code, I got the following horror show.


Where NUnit moaned about “The calling thread must be STA”. Oh, that’s to bad. So I had a small think, and then came up with this small idea, just pass the original code to a helper class and have it run that in a Thread using STA threading apartment state. Sounds cool, but did it work. Well yes actually it did, and here is the small helper class.


And here is how to use this from a NUnit test.


And just to prove it works, here is a screen shot of the actual test running successfully.


Here is a link to a small test project that you can see this working with in case you want to use this in your own projects.



This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Written By
Software Developer (Senior)
United Kingdom United Kingdom
I currently hold the following qualifications (amongst others, I also studied Music Technology and Electronics, for my sins)

- MSc (Passed with distinctions), in Information Technology for E-Commerce
- BSc Hons (1st class) in Computer Science & Artificial Intelligence

Both of these at Sussex University UK.


I am lucky enough to have won a few awards for Zany Crazy code articles over the years

  • Microsoft C# MVP 2016
  • Codeproject MVP 2016
  • Microsoft C# MVP 2015
  • Codeproject MVP 2015
  • Microsoft C# MVP 2014
  • Codeproject MVP 2014
  • Microsoft C# MVP 2013
  • Codeproject MVP 2013
  • Microsoft C# MVP 2012
  • Codeproject MVP 2012
  • Microsoft C# MVP 2011
  • Codeproject MVP 2011
  • Microsoft C# MVP 2010
  • Codeproject MVP 2010
  • Microsoft C# MVP 2009
  • Codeproject MVP 2009
  • Microsoft C# MVP 2008
  • Codeproject MVP 2008
  • And numerous codeproject awards which you can see over at my blog

Comments and Discussions

GeneralCOM object that has been separated from its underlying RCW cannot be used Pin
bibsoconner24-Nov-10 9:23
bibsoconner24-Nov-10 9:23 
GeneralRe: COM object that has been separated from its underlying RCW cannot be used Pin
Sacha Barber1-Dec-10 20:00
Sacha Barber1-Dec-10 20:00 
GeneralRequiresSTA attribute in Nunit 2.5 Pin
Martin Bohring17-Jun-09 4:54
Martin Bohring17-Jun-09 4:54 
GeneralRe: RequiresSTA attribute in Nunit 2.5 Pin
Sacha Barber17-Jun-09 8:45
Sacha Barber17-Jun-09 8:45 

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