How to Choose xUnit.net Runner Bitness (x86 and x64)

You clearly know that xUnit.net has many runners,

• Console runners
• Visual Studio runner
• Visual Studio for Mac/MonoDevelop runner

But if your unit test cases require certain bitness (x86 or x64), what should you do accordingly?

Console Runners

It cannot be any easier for console runners, as xUnit.net ships a console tool for x86 (xunit.console.x86.exe) and the other for x64 (xunit.console.exe). Here I show how I use them in Obfuscar CI script

If you are using .NET Core, then you probably know the command dotnet test you should use -a x64 or -a x86.

Visual Studio Runner

You would be surprised to notice that xUnit.net configuration does not cover bitness at all from its documentation. But that’s perfectly normal as Visual Studio has its builtin support, as documented in this article.

So by serving a .runsettings file, you can easily switch between x86 and x64,

<?xml version="1.0" encoding="utf-8"?>  
<RunSettings>  
  <!-- Configurations that affect the Test Framework -->  
  <RunConfiguration>  
    <!-- [x86] | x64    
      - You can also change it from menu Test, Test Settings, Default Processor Architecture -->  
      <TargetPlatform>x64</TargetPlatform>
  </RunConfiguration>  
</RunSettings>

Visual Studio for Mac/MonoDevelop Runner

Update in 2019: The following paragraphs were written when users needed to use a third party extension to run xUnit.net test cases in VS for Mac. Today, you should follow the following discussion instead.

As I am the current maintainer of the xUnit.net extension for these IDE products, I can confirm that before today you have no choice at all but to run the test cases in x86 only.

However, today two releases have been published (0.7.9 and 0.7.10) to fill this gap. The configuration is similar to Visual Studio, but with slight differences. To get started, you can create a file named xunit.runsettings in your unit test project to hold the same settings you use in Visual Studio. However, the file name must match exactly (as Visual Studio for Mac and MonoDevelop do not allow you to select any .runsettings file, so I decide to use a hardcoded name). If you decide not to use .runsettings file, then you can set an environment variable MONODEVELOP_XUNIT_RUNNER_BITNESS to x86 or x64. Finally, if neither .runsettings nor the environment variable is detected, the default behavior is to use the x64 runner.

Hope you enjoy the latest release.