The type or namespace name 'Fakes' does not exist in the namespace 'System' (are you missing an assembly reference?)

Hi @Pham Minh Tu ,

Thank you for taking time to post this issue in Microsoft Q&A forum.

It seems that there are something wrong with the assemblies(Fakes), maybe the versions, or some related files that generated before, under .NET Framework, but are not supported in .NET Core 3.1.

I suggest you try to remove the Fakes, the FakesAssemblies, the bin and obj folders in your project folder, then try to re-add the projects reference in VS (right-click the Dependencies > Add Project Reference… > Uncheck the project checkbox > OK > Do the same operations but this time check the project checkbox > OK).

After that re-add the Fakes Assembly(right-click the project under Dependencies , Projects > Add Fakes Assembly) and rebuild then rerun your project. Please remember to make a backup of your solution and then delete the folders.

In short, make a backup of your solution > delete Fakes, FakesAssemblies, bin and obj folders > re-add the project reference > re-add the Fakes Assembly > rebuild your unit test project > run the test.

Hope this helps.

Sincerely,
Tianyu

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Hi @Tianyu Sun-MSFT ,
Thank you for your response.

I will try it.

But I have other concern that I got the issue from fake of System library
System.Fake....

And I solved the following ways.

If I am wrong, please give me a solution.
Thank you.

Hello,

i have the same problem with Xunit under .NET 5. I'm not able to use shims there.

I added a new Xunit project for .NET 5, i went to Frameworks / Microsoft.NETCore.App, right click on System and "Add Fakes Assembly". VS added some packages and created a fakes folder.

]2

When i try to use shims for DateTime i got the message:
The type or namespace name 'Fakes' does not exist in the namespace 'System' (are you missing an assembly reference?)

Is it possible to use MS Fakes in XUnit under .NET 5 or .NET Core 3.1?

Sincerely
Johannes