从netcoreapp3.1升级到net6.0后单元测试无法运行

我有一个包含两个项目的解决方案：

• 主项目：基于netcoreapp3.1的ASP应用，已升级至net6.0
• 单元测试项目：同样从netcoreapp3.1升级至net6.0

升级后执行清理重建，构建无报错且显示成功，但出现以下问题：

• 右键单元测试项目时，“运行测试”选项呈灰色
• 在Test Explorer中运行测试，卡顿一段时间后提示未运行任何测试

错误输出信息 #

Aborting test discovery because a test run was requested.
Microsoft.VisualStudio.TestPlatform.ObjectModel.TestPlatformException: Failed to negotiate protocol, waiting for response timed out after 90 seconds. This may occur due to machine slowness, please set environment variable VSTEST_CONNECTION_TIMEOUT to increase timeout.
   at Microsoft.VisualStudio.TestPlatform.CommunicationUtilities.TestRequestSender.CheckVersionWithTestHost()
   at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Client.ProxyOperationManager.SetupChannel(IEnumerable`1 sources, String runSettings)
   at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Client.ProxyDiscoveryManager.DiscoverTests(DiscoveryCriteria discoveryCriteria, ITestDiscoveryEventsHandler2 eventHandler)
========== Test discovery aborted: 0 Tests found in 1.5 min ==========
Building Test Projects
Starting test discovery for requested test run
========== Starting test discovery ==========
Microsoft.VisualStudio.TestPlatform.ObjectModel.TestPlatformException: Failed to negotiate protocol, waiting for response timed out after 90 seconds. This may occur due to machine slowness, please set environment variable VSTEST_CONNECTION_TIMEOUT to increase timeout.
   at Microsoft.VisualStudio.TestPlatform.CommunicationUtilities.TestRequestSender.CheckVersionWithTestHost()
   at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Client.ProxyOperationManager.SetupChannel(IEnumerable`1 sources, String runSettings)
   at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Client.ProxyDiscoveryManager.DiscoverTests(DiscoveryCriteria discoveryCriteria, ITestDiscoveryEventsHandler2 eventHandler)
Executing all tests in project: Products.Dashboard.UnitTests
========== Test discovery aborted: 0 Tests found in 1.5 min ==========
========== Starting test run ==========
========== Test run finished: 0 Tests (0 Passed, 0 Failed, 0 Skipped) run in < 1 ms ==========
Resuming previously aborted test discovery
========== Starting test discovery ==========

单元测试项目文件内容 #

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>net6.0</TargetFramework>
    <ProjectGuid>{af563d15-3097-4430-89e5-6e80e6152dfa}</ProjectGuid>
    
    <IsPackable>false</IsPackable>
  </PropertyGroup>

  <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Debug|AnyCPU'">
    <PlatformTarget>x64</PlatformTarget>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.CodeCoverage" Version="16.10.0" />
    <PackageReference Include="Moq" Version="4.18.3" />
    <PackageReference Include="System.Text.Encoding.CodePages" Version="4.6.0" />
    <PackageReference Include="xunit" Version="2.4.2" />
    <PackageReference Include="xunit.runner.visualstudio" Version="2.4.1">
      <PrivateAssets>all</PrivateAssets>
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
    </PackageReference>
  </ItemGroup>

  <ItemGroup>
    <ProjectReference Include="..\..\src\MainProject.csproj" />
  </ItemGroup>

</Project>

尝试以下步骤逐一排查：

1. 更新测试相关NuGet包 #

当前xunit主包与runner版本不匹配（2.4.2 vs 2.4.1），且版本偏旧。更新到适配.NET 6的最新稳定版，确保主包和runner版本一致：

• 将xunit版本更新至2.5.3（或最新稳定版）
• 将xunit.runner.visualstudio版本更新至2.5.3
• 同步更新Microsoft.CodeCoverage到适配.NET 6的版本（如17.7.2）

更新后的PackageReference示例：

<PackageReference Include="Microsoft.CodeCoverage" Version="17.7.2" />
<PackageReference Include="xunit" Version="2.5.3" />
<PackageReference Include="xunit.runner.visualstudio" Version="2.5.3">
  <PrivateAssets>all</PrivateAssets>
  <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
</PackageReference>

2. 统一平台目标 #

确保解决方案内所有项目平台目标一致：

• 检查主项目的PlatformTarget设置，确保和测试项目同为x64
• 打开生成 > 配置管理器，将所有项目的平台统一设置为x64，避免AnyCPU与x64混合导致的兼容性问题

3. 清理测试缓存 #

• 删除解决方案目录下的.vs、bin、obj文件夹
• 执行清理解决方案，再重新生成解决方案
• 重启Visual Studio后尝试运行测试

4. 延长测试连接超时 #

按照错误提示设置环境变量延长超时：

• 右键单元测试项目 > 属性 > 调试 > 环境变量，添加VSTEST_CONNECTION_TIMEOUT=180（单位：秒）
• 或在系统环境变量中添加该配置，重启Visual Studio生效

5. 验证测试项目配置 #

• 确认项目文件顶部SDK设置为<Project Sdk="Microsoft.NET.Sdk">
• 删除项目文件中残留的netcoreapp3.1相关配置项

内容的提问来源于stack exchange，提问作者Andy