ℹ️

Summary and workarounds for the issue are below: #50950 (comment)

Describe the bug

When I run my .net Framework 4.8 NUnit tests with codecoverage on the commandline with .net 10 rc1 SDK Windows x64 installed, I get two times a message box with the title "dotnet.exe - System Error" and message "The code execution cannot proceed because covrun64.dll was not found. Reinstalling the program may fix this problem.

PS D:\Projects\CovRun64Repro\CovRun64Repro> dotnet test --collect:"Code Coverage"
Restore complete (0.2s)
    info NETSDK1057: You are using a preview version of .NET. See: https://aka.ms/dotnet-support-policy
  CovRun64Repro succeeded (0.1s) → bin\Debug\net48\CovRun64Repro.dll
NUnit Adapter 5.1.0.0: Test execution started
  CovRun64Repro                                                                                         Testing (39.7s)

The command does not continue until I press OK on the message box.

PS D:\Projects\CovRun64Repro\CovRun64Repro> dotnet test --collect:"Code Coverage"
Restore complete (0.2s)
    info NETSDK1057: You are using a preview version of .NET. See: https://aka.ms/dotnet-support-policy
  CovRun64Repro succeeded (0.1s) → bin\Debug\net48\CovRun64Repro.dll
NUnit Adapter 5.1.0.0: Test execution started
Running all tests in D:\Projects\CovRun64Repro\CovRun64Repro\bin\Debug\net48\CovRun64Repro.dll
   NUnit3TestExecutor discovered 1 of 1 NUnit test cases using Current Discovery mode, Non-Explicit run
NUnit Adapter 5.1.0.0: Test execution complete
  CovRun64Repro test succeeded (143.3s)

Test summary: total: 1; failed: 0; succeeded: 1; skipped: 0; duration: 143.3s
Build succeeded in 143.9s

Attachments:
  D:\Projects\CovRun64Repro\CovRun64Repro\TestResults\042aee28-3b04-4bc3-a9eb-fc430830c1ef\xxxxxx_xxxxxxxxx_2025-09-21.18_39_19.coverage

Expected Bahavior

The test should run with code coverage enabled without any system error or message box interruptions.

Regression

This issue does not occur when using the .NET 9.0.305 SDK. It only appears after installing the .NET 10.0.100-rc.1.25451.107 SDK. After installation of .net 10 rc1 the problem also appears when I try to use 9.0.305 explicitly with a global.json.

{
  "sdk": {
    "version": "9.0.305"
  }
}

To Reproduce

Run dotnet test --collect:"Code Coverage" for the following test project:
CovRun64Repro.csproj

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net48</TargetFramework>
    <IsPackable>false</IsPackable>
    <IsTestProject>true</IsTestProject>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
    <PackageReference Include="NUnit" Version="4.4.0" />
    <PackageReference Include="NUnit.Analyzers" Version="4.10.0">
      <PrivateAssets>all</PrivateAssets>
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
    </PackageReference>
    <PackageReference Include="NUnit3TestAdapter" Version="5.1.0" />
  </ItemGroup>
</Project>

Tests.cs:

using NUnit.Framework;
public class Tests
{
    [Test]
    public void Test1()
    {
        Assert.Pass();
    }
}

Further technical details

.NET SDK:
 Version:           10.0.100-rc.1.25451.107
 Commit:            2db1f5ee2b
 Workload version:  10.0.100-manifests.0e2d47c4
 MSBuild version:   17.15.0-preview-25451-107+2db1f5ee2

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.26100
 OS Platform: Windows
 RID:         win-x64
 Base Path:   C:\Program Files\dotnet\sdk\10.0.100-rc.1.25451.107\

.NET workloads installed:
There are no installed workloads to display.
Configured to use workload sets when installing new manifests.
No workload sets are installed. Run "dotnet workload restore" to install a workload set.

Host:
  Version:      10.0.0-rc.1.25451.107
  Architecture: x64
  Commit:       2db1f5ee2b

.NET SDKs installed:
  9.0.305 [C:\Program Files\dotnet\sdk]
  10.0.100-rc.1.25451.107 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 9.0.9 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 10.0.0-rc.1.25451.107 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 9.0.9 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 10.0.0-rc.1.25451.107 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 9.0.9 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 10.0.0-rc.1.25451.107 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Other architectures found:
  None

Environment variables:
  Not set

global.json file:
  Not found

Learn more:
  https://aka.ms/dotnet/info

• I run from command line
• I first discovered the problem after I had installed VisualStudio 2026 Insider Pro (first the release that had no version number in the installer, then updated to version 11012.119). I then uninstalled VisualStudio 2026 and .net 10 rc1. Did not solve the Problem and left me with a broken dotnet setup.

• Because of this I removed also Visual Studio 2022 pro (17.14.15), .net 9.0.305 SDK and all dotnet runtime I had installed.
• reboot
• After the reboot I just installed .net 9.0.305 SDK. With this SDK the command runs without the message box.
• I then installed .net 10.0.100-rc.1.25451.107 SDK again and the message box appeared again.