Skip to main content

Testing waithandles in MSTest

For a client I needed to write a parallel execution mechanism that executes multiple tasks at the same time on different threads but further execution had to wait before all threads signals complete. In this situation, synchronization becomes very important,  so I used the WaitHandle classes to implement this functionality. As no code is complete without good unit tests, I added a test to validate the behavior of the waithandles:

   1:  [TestMethod]
   2:  public void Waithandle_Should_Wait_Until_All_Tasks_Complete()
   3:  {    
   4:     Action task1 = ()=> DoSomething();
   5:     Action task2 = ()=> DoSomething();
   6:     Action task3 = ()=> DoSomething();
   7:   
   8:     IAsyncResult result1= task1.BeginInvoke(null, null, null);   
   9:     IAsyncResult result2= task2.BeginInvoke(null, null, null);   
  10:     IAsyncResult result3= task3.BeginInvoke(null, null, null);      
  11:   
  12:     WaitHandle.WaitAll(new WaitHandle[]{result1.AsyncWaitHandle, result2.AsyncWaitHandle, result3.AsyncWaitHandle});     
  13:     // Asserts go here...
  14:  }


In this example,  WaitHandle.WaitAll stops any further execution until all tasks complete.


The only problem is that when you try to run this test, it fails with the following error message: Test method Ordina.ParallelRunner.Waithandle_Should_Wait_Until_All_Tasks_Completethrew exception:  System.NotSupportedException: WaitAll for multiple handles on a STA thread is not supported..


This is actually documented behavior on the part of WaitHandle.WaitAll. It seems that MSTest runs in an STA by default.


Fortunately, this is configurable and can be edited in your .testrunconfig file. There's no user interface for this setting, so you will have to open the file and  add this line to make MSTest run in an MTA. 

   1:  <ExecutionThread apartmentState="1" />

By default, the value of this element is 0 (which is equivalent to ApartmentState.STA - the default value of the enumeration), but as you can see, I've changed it to 1 (which is equivalent to ApartmentState.MTA). After saving this change, the test now succeeds.

Labels:

Popular posts from this blog

Podman– Command execution failed with exit code 125

After updating WSL on one of the developer machines, Podman failed to work. When we took a look through Podman Desktop, we noticed that Podman had stopped running and returned the following error message: Error: Command execution failed with exit code 125 Here are the steps we tried to fix the issue: We started by running podman info to get some extra details on what could be wrong: >podman info OS: windows/amd64 provider: wsl version: 5.3.1 Cannot connect to Podman. Please verify your connection to the Linux system using `podman system connection list`, or try `podman machine init` and `podman machine start` to manage a new Linux VM Error: unable to connect to Podman socket: failed to connect: dial tcp 127.0.0.1:2655: connectex: No connection could be made because the target machine actively refused it. That makes sense as the podman VM was not running. Let’s check the VM: >podman machine list NAME         ...
Read more

Azure DevOps/ GitHub emoji

I’m really bad at remembering emoji’s. So here is cheat sheet with all emoji’s that can be used in tools that support the github emoji markdown markup: All credits go to rcaviers who created this list.
Read more

VS Code Planning mode

After the introduction of Plan mode in Visual Studio , it now also found its way into VS Code. Planning mode, or as I like to call it 'Hannibal mode', extends GitHub Copilot's Agent Mode capabilities to handle larger, multi-step coding tasks with a structured approach. Instead of jumping straight into code generation, Planning mode creates a detailed execution plan. If you want more details, have a look at my previous post . Putting plan mode into action VS Code takes a different approach compared to Visual Studio when using plan mode. Instead of a configuration setting that you can activate but have limited control over, planning is available as a separate chat mode/agent: I like this approach better than how Visual Studio does it as you have explicit control when plan mode is activated. Instead of immediately diving into execution, the plan agent creates a plan and asks some follow up questions: You can further edit the plan by clicking on ‘Open in Editor’: ...
Read more