Could not load file or assembly 'Microsoft.VisualStudio.TestPlatform.ObjectModel, Version=11.0.0.0'

user_3122378 0
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I am using MSTest.TestAdapter and MSTest.TestFramework both version 1.2.0 for my MS tests unit tests. On my local machine (Visual Studio 2017) the tests run perfectly, but on our build server we get this message:

Could not load file or assembly 'Microsoft.VisualStudio.TestPlatform.ObjectModel, Version=11.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified.

Then I checked the reference of this assembly with ildasm, and indeed it is the 11.0.0.0 version (see below)

However I cannot find the v11 of this assembly, online there is only the v14 version on nuget: https://www.nuget.org/packages/Microsoft.VisualStudio.TestPlatform.ObjectModel/

I also searched on my machine and I couldn't find the v11.

So my question, why does the tests run on my machine and not on the build server?

I tried assembly binding but without success.

enter image description here

assembly-loading mstest unit-testing .net c#
7 Answers

Same issue, I was able to install the latest version:

Install-Package Microsoft.TestPlatform.ObjectModel -Version 15.8.0

Then add a binding redirect to the test projects app.config:

    <runtime>
        <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
            <dependentAssembly>
                <assemblyIdentity name="Microsoft.VisualStudio.TestPlatform.ObjectModel" publicKeyToken="b03f5f7f11d50a3a" culture="neutral" />
                <bindingRedirect oldVersion="11.0.0.0-14.0.0.0" newVersion="15.0.0.0" />
            </dependentAssembly>
        </assemblyBinding>
    </runtime>
user_18671570
user_27924140

In the test output window I had errors like this…

[MSTest][Discovery][C:\Repos\Flomaster\bin\Debug\ApiTest.UnitMaintenance.dll] Failed to discover tests from assembly C:\Repos\Flomaster\bin\Debug\ApiTest.UnitMaintenance.dll. Reason:Type 'Microsoft.VisualStudio.TestPlatform.ObjectModel.Trait' in Assembly 'Microsoft.VisualStudio.TestPlatform.ObjectModel, Version=15.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' is not marked as serializable.

I managed to get my test runners working by Cleaning out all my obj and bin\debug folders, but it came back so I looked a bit deeper and found that just searching for Microsoft.VisualStudio.TestPlatform.ObjectModel.dll and removing any matching files was enough to get the test runner working

user_36359740

Faced the same error after having mistakenly added the NuGet package for NUnit 3.0 to several projects in the solution and then removing it.

The reference didn't get removed completely. I had to open each .csproj file manually and delete all references to the previously removed NuGet package. After a clean and rebuild, the error went away.

user_36142110

Same problem. Solve by including the adapter locaters in the .proj files:

<PackageReference Include="MSTest.TestAdapter" Version="2.2.10" />
<PackageReference Include="MSTest.TestFramework" Version="2.2.10" />
user_4413570
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