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

C# Problem Overview

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.

C# Solutions

Solution 1 - C#

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

Solution 2 - C#

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.

Solution 3 - C#

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 4 - C#

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 5 - C#

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 6 - C#

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 7 - C#

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 8 - C#

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 9 - C#

Fixed it by installing xunit.runner.visualstudio.

Solution 10 - C#

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 - C#

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 12 - C#

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 13 - C#

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 14 - C#

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 15 - C#

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 16 - C#

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 17 - C#

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 18 - C#

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 19 - C#

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 20 - C#

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 21 - C#

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 22 - C#

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.

Content Type	Original Author	Original Content on Stackoverflow
Question	Matt W	View Question on Stackoverflow
Solution 1 - C#	R15	View Answer on Stackoverflow
Solution 2 - C#	Andreas	View Answer on Stackoverflow
Solution 3 - C#	Matt W	View Answer on Stackoverflow
Solution 4 - C#	Willy Van den Driessche	View Answer on Stackoverflow
Solution 5 - C#	Maximiliano Rios	View Answer on Stackoverflow
Solution 6 - C#	Dev Leader	View Answer on Stackoverflow
Solution 7 - C#	SteveHansen	View Answer on Stackoverflow
Solution 8 - C#	Raj kumar	View Answer on Stackoverflow
Solution 9 - C#	Eugene Ihnatsyeu	View Answer on Stackoverflow
Solution 10 - C#	Michael Armitage	View Answer on Stackoverflow
Solution 11 - C#	Äkwav	View Answer on Stackoverflow
Solution 12 - C#	Hakakou	View Answer on Stackoverflow
Solution 13 - C#	Jpsy	View Answer on Stackoverflow
Solution 14 - C#	Blisco	View Answer on Stackoverflow
Solution 15 - C#	SaifAli Sanadi	View Answer on Stackoverflow
Solution 16 - C#	S1r-Lanzelot	View Answer on Stackoverflow
Solution 17 - C#	reim	View Answer on Stackoverflow
Solution 18 - C#	Venu	View Answer on Stackoverflow
Solution 19 - C#	ihebiheb	View Answer on Stackoverflow
Solution 20 - C#	Shawon Barua	View Answer on Stackoverflow
Solution 21 - C#	Aislan Gelatti Rocha	View Answer on Stackoverflow
Solution 22 - C#	tmndungu	View Answer on Stackoverflow