If you want to run NUnit tests with MSBuild, then you need to download and install the MSBuild Community tasks. This allows you to create a unit test target like this:

  <TestAssembly Include="ClientBin\*Tests.dll" />
<Target Name="Test" DependsOnTargets="Build">
  <NUnit Assemblies="@(TestAssembly)"
         ToolPath="C:\Program Files\NUnit 2.5.5\bin\net-2.0"

(Most examples don’t show the need to specify a ToolPath, but I have found I need it, perhaps because it isn’t in my Path?)

The trouble is, if the assemblies containing the unit tests have been build with the .NET 4 framework, you will get the following error:

C:\Program Files\NUnit 2.5.5\bin\net-2.0\nunit-console.exe /nologo ClientBin\
ProcessModel: Default    DomainUsage: Single
Execution Runtime: net-2.0
Unhandled Exception:
System.BadImageFormatException: Could not load file or assembly 'D:\TFS\Trial
\Inform5\ClientBin\Client.Tests.dll' or one of its dependencies.
This assembly is built by a runtime newer than the currently loaded runtime a
nd cannot be loaded.
File name: 'D:\TFS\Trial\Inform5\ClientBin\Client.Tests.dll'

What is needed is to ensure that nunit-console.exeruns against the .NET 4 framework. The way I achieved this was to make a copy of the net-2.0folder that comes with NUnit 2.5.5 and rename it to net-4.0(n.b. make sure the libfolder comes along too as nunit-console.exe depends on its contents). Then, I edited the nunit-console.exe.config file to have the following contents (the key bit is to add the supportedRuntime setting):

<?xml version="1.0" encoding="utf-8"?>
  <!-- Set the level for tracing NUnit itself -->
  <!-- 0=Off 1=Error 2=Warning 3=Info 4=Debug -->
       <add name="NTrace" value="0" />

    <supportedRuntime version="v4.0"/>

    <!-- We need this so test exceptions don't crash NUnit -->
    <legacyUnhandledExceptionPolicy enabled="1" />

    <!-- Look for addins in the addins directory for now -->
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <probing privatePath="lib;addins"/>

Now all that is needed is to update the ToolPathin the MSBuild script to point to the new location

<Target Name="Test" DependsOnTargets="Build">
  <NUnit Assemblies="@(TestAssembly)"
        ToolPath="C:\Program Files\NUnit 2.5.5\bin\net-4.0"

I’d be interested in hearing if there is an easier way of solving this problem though, as I don’t really want to have to require all developers to manually perform these steps on their machine.

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Comment by Travis Laborde

When I faced that, I just decided to switch to the "exec" task.

This allowed me to add the /framework argument easily, like so:


Travis Laborde
Comment by Mark H

thanks for this suggestion Travis, will give this a try

Comment by Anonymous

Hi Travis - thanks for the post. Saved me a couple of hours.

Comment by Anonymous

Thanks It worked

Comment by Len Rivers

I'm using the MSBuild sprinter to run my assessments, but with the deficiency of xunit.net assistance have no way to show the outcomes.

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