Unable to find testhost.dll. Please publish your t

Question

I have a simple dotnet core class library with a single XUnit test method:

TestLib.csproj:
<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>netstandard2.0</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.NET.Test.SDK" Version="15.9.0" />
    <PackageReference Include="xunit" Version="2.4.1" />
    <PackageReference Include="xunit.runner.console" Version="2.4.1">
      <IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>
      <PrivateAssets>all</PrivateAssets>
    </PackageReference>
    <PackageReference Include="xunit.runner.visualstudio" Version="2.4.1">
      <IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>
      <PrivateAssets>all</PrivateAssets>
    </PackageReference>
    <PackageReference Include="xunit.runners" Version="2.0.0" />
  </ItemGroup>

</Project>

BasicTest.cs:
using Xunit;

namespace TestLib
{
    public class BasicTest
    {
        [Fact(DisplayName = "Basic unit test")]
        [Trait("Category", "unit")]
        public void TestStringHelper()
        {
            var sut = "sut";
            var verify = "sut";

            Assert.Equal(sut, verify);
        }
    }
}

If I enter the project on the CLI and type dotnet build the project builds. If I type dotnet test I get this:

C:\git\Testing\TestLib> dotnet test
C:\git\Testing\TestLib\TestLib.csproj : warning NU1701: Package 'xunit.runner.visualstudio 2.4.1' was restored using '.NETFramework,Version=v4.6.1' instead of the project target framework '.NETStandard,Version=v2.0'. This package may not be fully compatible with your project.
Build started, please wait...
C:\git\Testing\TestLib\TestLib.csproj : warning NU1701: Package 'xunit.runner.visualstudio 2.4.1' was restored using '.NETFramework,Version=v4.6.1' instead of the project target framework '.NETStandard,Version=v2.0'. This package may not be fully compatible with your project.
Build completed.

Test run for C:\git\Testing\TestLib\bin\Debug\netstandard2.0\TestLib.dll(.NETStandard,Version=v2.0)
Microsoft (R) Test Execution Command Line Tool Version 16.0.0-preview-20181205-02
Copyright (c) Microsoft Corporation.  All rights reserved.

Starting test execution, please wait...
Unable to find C:\git\Testing\TestLib\bin\Debug\netstandard2.0\testhost.dll. Please publish your test project and retry.

Test Run Aborted.

What do I need to change to get the test to run?

If it helps, VS Code is not displaying the tests in its test explorer, either.

Answer 1

In my case the problem was that I have an extension project for xunit. There is also a test project to test the extensions. When I ran dotnet test on my solution, my extension project was also picked up as a unit test project (it took me some time to realize this). The reason for this is that it references some xunit packages. One of these xunit packages automatically sets the <IsTestProject>true</IsTestProject> property in you csprj file. This is actually a good thing since 99.99% of the projects that reference xunit are actually unit tests. I could finally solve this by explicitly setting

     <PropertyGroup>
...
        <IsTestProject>false</IsTestProject>
...
      </PropertyGroup>

Manually in my csproj file. Then the problem went away.

Answer 2

In my case, the problem was that I was targeting .NET Core 2.0 and switching to .NET Core 2.1 solved the problem. However I was using Microsoft.NET.Test.SDK v16.4.0 instead of 15.9.0.

Answer 3

Ran into this error, the root cause was the tests were hitting the maximum length for a Windows path (MAX_PATH), which is defined as 260 characters.

Answer 4

same issue i faced for Nunit (.net core 3.1) project . I was using Microsoft.NET.Test.SDK v16.6.1, I downgraded the version to 15.9.0. And it start working

Answer 5

If you are targeting netstandard2.0 this will not work. If are using .NET Core. make sure the .csproj contains the following lines:

<TargetFramework>netcoreapp3.0</TargetFramework>

and also contains the package Microsoft.NET.Test.Sdk

Answer 6

Installing Microsoft.NET.Test.Sdk package from nuget package manager solved my issue.