'Unable to find testhost.dll. Please publish your test project and retry

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.

Solution 1:^[1]

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

Solution 2:^[2]

I had created a class library and tried to use the XUnit NuGet package in it.

What I should have done was created an XUnit project using this command: dotnet new xunit -n TestProject

I found this helpful page.

Solution 3:^[3]

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.

Solution 4:^[4]

I found a very interesting compatibility issue with a version. I did upgrade just as a normal practice, my code, and I switched to xUnit.runner.visualstudio 2.4.2. It stopped working for .Net Core 3.1. I had to downgrade to 2.4.1 and it started working again.

Additional information after one of my comments.

The package xunit.runner.visualstudio versions <= 2.4.1 includes a reference to Microsoft.NET.Test.Sdk. Later versions don't, so you need to add the reference to your project.

See https://stackoverflow.com/a/63786758/3248302

Solution 5:^[5]

I've encountered this a couple of times and I always forget what's up. Most recently I had:

Class Library -> Targeting .NET Core 3.0
Test Project -> Targeting .NET Core 3.1

Packages for my test project:

Moq -> 4.14.1
xUnit -> 2.4.1
xUnit.Runner.VisualStudio -> 2.4.2

I was seeing:

Unable to find C:\PATH\bin\Debug\netstandard2.0\testhost.dll. Please publish your test project and retry.

And all that I needed to do was add to my test project the missing nuget package: "Microsoft.NET.Test.SDK"

Everything was back to normal at this point.

Solution 6:^[6]

This happened to me after updating Microsoft.NET.Test.Sdk from v16.2.0 to v16.4.0 with <TargetFramework>netcoreapp2.0</TargetFramework>. Updating to <TargetFramework>netcoreapp3.0</TargetFramework> resolved the issue for me.

Solution 7:^[7]

If you are using xUnit, make sure your project type is not as netstanderd. As xUnit doesn't support netstanderd, change it to coreapp2.0 or others.

Solution 8:^[8]

Fixed it by installing xunit.runner.visualstudio.

Solution 9:^[9]

Had to add Microsoft.TestPlatform.TestHost to get testhost.dll. I found that in this answer https://github.com/dotnet/sdk/issues/7171#issuecomment-261506546

Solution 10:^[10]

I was building a netcoreapp2.2 test project and then trying to run dotnet vstest from the bin folder. I noticed that the Microsoft Test DLLs from:

<PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.0.1" />

were not being output to my bin folder. Instead of just building, I ran a publish instead which did include the necessary DLLs in the output folder and I was then able to run dotnet vstest from there.

Solution 11:^[11]

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

Solution 12:^[12]

I found 5 factors to be crucial.
(3 of whom were spread throughout the other answers here in mixed variations.)

1 to 4:
Add these Nuget Packages in versions that work for your .NET Core version:

xunit
Microsoft.NET.Test.Sdk
xunit.runner.visualstudio
Microsoft.AspNetCore.Mvc.Testing

5:
Now make sure that Microsoft.NET.Test.Sdk is set to NOT ExcludeAssets. To do so use one of these methods:

In Project Explorer go to Dependencies –> NuGet and find the Sdk package. Right click it and select "Properties". Remove "All" from the field ExcludeAssets.
Alternatively edit your .csproj file and remove ExcludeAssets="All" from the Sdk package entry, if present:

<!-- Bad: -->
<PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.11.0" ExcludeAssets="All" />
<!-- Good: -->
<PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.11.0" />

Solution 13:^[13]

This error can occur if you upgrade xunit.runner.visualstudio to a version greater than 2.4.1. Versions up to and including 2.4.1 include a reference to Microsoft.NET.Test.Sdk but later ones don't, so you need to include the reference in your own project.

Interestingly, I found that NCrunch still ran my tests without the additional reference, even though I couldn't run them via the CLI.

Solution 14:^[14]

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

Solution 15:^[15]

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.

Solution 16:^[16]

This could also be caused by inadvertently trying to run a non-test project, this usually happens when your test files filter is too wide.

Solution 17:^[17]

Got this error, when trying to debug a unit test. Below are the steps I tried.

Step 1: Installed Microsof.TestPlatform.TestHost and tried to run the test but no luck.
Step 2: Changed Target framework from .NET Core 2.0 to 2.1 and tried to run the test but no luck.
Step 3: Closed and opened VS2017 and tried to run.

Yay!!! it worked :-) Never miss to try the last step ;-) Hope this helps someone like me.

Solution 18:^[18]

In my case it was a silly mistake. I was referencing xunit also in my source project (not only in my test project)

Deleting the xunit dependency in my source project fixed the problem.

Solution 19:^[19]

If you are running a project by cloning than Solution is to install the Microsoft.NET.Test.Sdk. How to : Tools>Nuget Package Manager>Manage Nuget Packages For Solution...>Search for Microsoft.NET.Test.Sdk and install for your test project.

Solution 20:^[20]

In my case, it was necessary to include a reference to MsTest.TestAdapter module using nuget.

A fresh project with MSTest.TestFramework and Microsoft.Net.Test.Sdk was not enough to run a single unit test.

Noticing in my case I was using a test project targeting .NET framework 4.8 and not .NET core. Although, I strongly believe this fix might apply to that platform as well

Solution 21:^[21]

I was using .NET Core Framework 6.0 I had to downgrade Microsoft.NET.Test.Sdk from Version 17.1.0 to 16.5.0 to resolve the issue.

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution	Source
Solution 1	R15
Solution 2	Matt W
Solution 3	Willy Van den Driessche
Solution 4	RonC
Solution 5	Dev Leader
Solution 6	SteveHansen
Solution 7	Raj kumar
Solution 8	Eugene Ihnatsyeu
Solution 9
Solution 10	Michael Armitage
Solution 11	Hakakou
Solution 12	Jpsy
Solution 13
Solution 14	SaifAli Sanadi
Solution 15	S1r-Lanzelot
Solution 16	reim
Solution 17	Venu
Solution 18	ihebiheb
Solution 19	Shawon Barua
Solution 20	Aislan Gelatti Rocha
Solution 21	tmndungu

'Unable to find testhost.dll. Please publish your test project and retry

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