本地VS2022单元测试正常，流水线运行时加载StringEx类型失败

本地使用Visual Studio 2022运行单元测试完全正常，但在Azure DevOps流水线执行相同测试时抛出以下错误：

[error]An exception occurred while invoking executor 'executor://mstestadapter/v2': Could not load type 'Microsoft.VisualStudio.TestTools.UnitTesting.StringEx' from assembly 'Microsoft.VisualStudio.TestPlatform.TestFramework, Version=14.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'.

完整堆栈跟踪：

##[debug]Processed: ##vso[task.logissue type=error;]An exception occurred while invoking executor 'executor://mstestadapter/v2': Could not load type 'Microsoft.VisualStudio.TestTools.UnitTesting.StringEx' from assembly 'Microsoft.VisualStudio.TestPlatform.TestFramework, Version=14.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'.
##[error]Stack trace:
##[debug]Processed: ##vso[task.logissue type=error;]Stack trace:
##[error]   at Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.MSTestSettings.PopulateSettings(IDiscoveryContext context)
##[debug]Processed: ##vso[task.logissue type=error;]   at Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.MSTestSettings.PopulateSettings(IDiscoveryContext context)
##[error]   at Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.MSTestExecutor.RunTests(IEnumerable`1 sources, IRunContext runContext, IFrameworkHandle frameworkHandle)
##[debug]Processed: ##vso[task.logissue type=error;]   at Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.MSTestExecutor.RunTests(IEnumerable`1 sources, IRunContext runContext, IFrameworkHandle frameworkHandle)
##[error]   at Microsoft.VisualStudio.TestPlatform.Common.ExtensionDecorators.SerialTestRunDecorator.RunTests(IEnumerable`1 sources, IRunContext runContext, IFrameworkHandle frameworkHandle)
##[debug]Processed: ##vso[task.logissue type=error;]   at Microsoft.VisualStudio.TestPlatform.Common.ExtensionDecorators.SerialTestRunDecorator.RunTests(IEnumerable`1 sources, IRunContext runContext, IFrameworkHandle frameworkHandle)
##[error]   at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Execution.RunTestsWithSources.InvokeExecutor(LazyExtension`2 executor, Tuple`2 executorUriExtensionTuple, RunContext runContext, IFrameworkHandle frameworkHandle)
##[debug]Processed: ##vso[task.logissue type=error;]   at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Execution.RunTestsWithSources.InvokeExecutor(LazyExtension`2 executor, Tuple`2 executorUriExtensionTuple, RunContext runContext, IFrameworkHandle frameworkHandle)
##[error]   at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Execution.BaseRunTests.<>c__DisplayClass46_0.<RunTestInternalWithExecutors>b__0()
##[debug]Processed: ##vso[task.logissue type=error;]   at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Execution.BaseRunTests.<>c__DisplayClass46_0.<RunTestInternalWithExecutors>b__0()
##[error]   at Microsoft.VisualStudio.TestPlatform.PlatformAbstractions.PlatformThread.<>c__DisplayClass0_0.<Run>b__0()
##[debug]Processed: ##vso[task.logissue type=error;]   at Microsoft.VisualStudio.TestPlatform.PlatformAbstractions.PlatformThread.<>c__DisplayClass0_0.<Run>b__0()
##[error]--- End of stack trace from previous location where exception was thrown ---
##[debug]Processed: ##vso[task.logissue type=error;]--- End of stack trace from previous location where exception was thrown ---
##[error]   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
##[debug]Processed: ##vso[task.logissue type=error;]   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
##[error]   at Microsoft.VisualStudio.TestPlatform.PlatformAbstractions.PlatformThread.Run(Action action, PlatformApartmentState apartmentState, Boolean waitForCompletion)
##[debug]Processed: ##vso[task.logissue type=error;]   at Microsoft.VisualStudio.TestPlatform.PlatformAbstractions.PlatformThread.Run(Action action, PlatformApartmentState apartmentState, Boolean waitForCompletion)
##[error]   at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Execution.BaseRunTests.TryToRunInStaThread(Action action, Boolean waitForCompletion)
##[debug]Processed: ##vso[task.logissue type=error;]   at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Execution.BaseRunTests.TryToRunInStaThread(Action action, Boolean waitForCompletion)
##[error]   at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Execution.BaseRunTests.RunTestInternalWithExecutors(IEnumerable`1 executorUriExtensionMap, Int64 totalTests)
##[debug]Processed: ##vso[task.logissue type=error;]   at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Execution.BaseRunTests.RunTestInternalWithExecutors(IEnumerable`1 executorUriExtensionMap, Int64 totalTests)
[xUnit.net 00:00:00.00] xUnit.net VSTest Adapter v2.4.1 (64-bit .NET Framework 4.8.4300.0)

流水线测试步骤配置：

- task: VSTest@2
  displayName: 'Run unit tests'
  condition: and(succeeded(), eq('${{ parameters.enableTests }}', 'true'))
  inputs:
    #vstestLocationMethod: location
    #vstestLocation: 'C:\Program Files\PackageManagement\NuGet\Packages\Microsoft.TestPlatform.16.4.0\tools\net451\Common7\IDE\Extensions\TestPlatform'
    #vstestLocation: 'C:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools\Common7\IDE\Extensions\TestPlatform'
    testSelector: 'testAssemblies'
    vsTestVersion: 'toolsInstaller'
    testAssemblyVer2: '**\\*UnitTests*.dll'
    platform: '${{ parameters.buildPlatform }}'
    configuration: '${{ parameters.buildConfiguration }}'
    searchFolder: '$(build.ArtifactStagingDirectory)\\${{parameters.packageFolderName}}'
    codeCoverageEnabled: '${{ parameters.enableCodeCoverage }}'
    runInParallel: "true"
    testFiltercriteria: "TestCategory!=Manual"

已尝试调整MSTest.TestAdapter、MSTest.TestFramework版本及.NET SDK，但问题未解决。

1. 统一MSTest适配器与测试框架版本到最新稳定版 #

确保项目中MSTest.TestAdapter和MSTest.TestFramework的版本完全一致，且升级到最新稳定版（比如2.2.10或更高）。在项目的NuGet包管理器中更新这两个包，避免版本不兼容导致的类型缺失。

2. 指定流水线使用与本地一致的VS测试平台版本 #

流水线中vsTestVersion: 'toolsInstaller'会自动安装最新测试平台，可能与本地VS2022使用的版本不匹配。可改为指定使用Visual Studio 2022的测试平台：

vsTestVersion: 'latest'
# 或明确指定版本
# vsTestVersion: '17.x'

如果构建代理安装了VS2022 Build Tools，也可直接指定测试平台路径：

vstestLocationMethod: 'location'
vstestLocation: 'C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\Common7\IDE\Extensions\TestPlatform'

3. 确保测试程序集的依赖文件被正确发布到流水线工件 #

检查构建步骤是否将MSTest.TestAdapter.dll、MSTest.TestFramework.dll等依赖文件复制到测试程序集所在目录。可添加Copy Files步骤：

- task: CopyFiles@2
  displayName: 'Copy test dependencies'
  inputs:
    SourceFolder: '$(SolutionDir)\packages\MSTest.TestAdapter.*\build\_common'
    Contents: '**/*.dll'
    TargetFolder: '$(build.ArtifactStagingDirectory)\${{parameters.packageFolderName}}'

4. 临时禁用并行测试排查冲突 #

流水线开启的runInParallel: "true"可能引发依赖加载冲突，可临时禁用验证：

runInParallel: "false"

5. 检查测试程序集的目标框架版本 #

确保测试项目的目标框架与流水线使用的.NET SDK版本兼容，比如本地用.NET Framework 4.8，流水线也要匹配对应SDK版本，避免跨框架加载问题。

内容的提问来源于stack exchange，提问作者Raulster24