.NET 6 Test Project with CopyLocalLockFileAssemblies = false fails running tests

[remoba]

Describe the bug

When upgrading a test project that uses .NET 5 that has CopyLocalLockFileAssemblies set to false to .NET 6, dotnet test stops working on my machine with an error about not finding Microsoft.TestPlatform.CoreUtilities

Downgrading the target back to .NET 5, or removing the CopyLocalLockFileAssemblies=false tag both get it to work.

To Reproduce

1. Create a new directory
2. Save the following csproj into the directory

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net6.0</TargetFramework>
    <CopyLocalLockFileAssemblies>false</CopyLocalLockFileAssemblies>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.3.0" />
    <PackageReference Include="xunit" Version="2.4.2" />
    <PackageReference Include="xunit.runner.visualstudio" Version="2.4.5">
      <PrivateAssets>all</PrivateAssets>
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
    </PackageReference>
    <DotNetCliToolReference Include="dotnet-xunit" Version="2.3.1" />
  </ItemGroup>
</Project>

3. Open a command window in said directory
4. Run dotnet test

Exceptions (if any)

C:\MyTests>dotnet test
  Determining projects to restore...
  Restored C:\MyTests\MyTests.csproj (in 943 ms).
  1 of 2 projects are up-to-date for restore.
  MyTests -> C:\MyTests\bin\Debug\net6.0\MyTests.dll
Test run for C:\MyTests\bin\Debug\net6.0\MyTests.dll (.NETCoreApp,Version=v6.0)
Microsoft (R) Test Execution Command Line Tool Version 17.2.0 (x64)
Copyright (c) Microsoft Corporation.  All rights reserved.

Starting test execution, please wait...
A total of 1 test files matched the specified pattern.
Testhost process exited with error: Unhandled exception. System.IO.FileNotFoundException: Could not load file or assembly 'Microsoft.TestPlatform.CoreUtilities, Version=15.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. The system cannot find the file specified.
File name: 'Microsoft.TestPlatform.CoreUtilities, Version=15.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'
   at Microsoft.VisualStudio.TestPlatform.TestHost.Program.Main(String[] args)
. Please check the diagnostic logs for more information.

Test Run Aborted.

Further technical details

• Include the output of dotnet --info

C:\MyTests>dotnet --info
.NET SDK (reflecting any global.json):
 Version:   6.0.301
 Commit:    43f9b18481

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.22000
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\6.0.301\

Host (useful for support):
  Version: 6.0.6
  Commit:  7cca709db2

.NET SDKs installed:
  3.1.422 [C:\Program Files\dotnet\sdk]
  5.0.408 [C:\Program Files\dotnet\sdk]
  5.0.409 [C:\Program Files\dotnet\sdk]
  6.0.301 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 3.1.26 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.28 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 5.0.17 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 6.0.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 3.1.26 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.28 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 5.0.17 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 6.0.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 3.1.26 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 3.1.28 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 5.0.17 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 6.0.6 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

To install additional .NET runtimes or SDKs:
  https://aka.ms/dotnet-download

• The IDE (VS / VS Code/ VS4Mac) you're running on, and its version
  I have Visual Studio 2022 17.2.5 installed , but this reproduces outside of Visual Studio

Running this on a Windows 11 machine

[remoba]

I have found that adding this to the first property group fixes the issue.

<GenerateRuntimeConfigDevFile>true</GenerateRuntimeConfigDevFile>

I guess the behavior for this property changed to false by default in .NET 6. I wasn't aware this is a requirement. Is it mandatory now when using CopyLocalLockFileAssemblies=false?

[nohwnd]

I don't think this is documented as mandatory anywhere, and we don't have any special handling of this case in test platform. Glad you figured it out.