Azure Pipeline Error: vstest.console process failed to connect to testhost process - .net-core

Question

I am converting my azure pipeline to YAML pipeline. When I trigger the build, it gets failed on the Unit test step and gives the error as below
[error]vstest.console process failed to connect to testhost process after 90 seconds. This may occur due to machine slowness, please set environment variable VSTEST_CONNECTION_TIMEOUT to increase timeout.
I could not find a way to add the VSTEST_CONNECTION_TIMEOUT value anywhere. Could you please help me with this.
Here is the sample .yml I am using
- task: VSTest#2
displayName: 'Test'
inputs:
testAssemblyVer2: '**\bin\**\Tests.dll'
testFiltercriteria: 'TestCategory=Unit'
runSettingsFile: XYZ.Tests/codecoverage.runsettings
codeCoverageEnabled: true
platform: '$(BuildPlatform)'
configuration: '$(BuildConfiguration)'
diagnosticsEnabled: true

Answer 1

I would recommend you to use the dotnetCli task instead. It is shorter, clearer and straight forward (It will have the "same" effect as executing dotnet test in your console)
- task: DotNetCoreCLI#2
displayName: 'Run tests'
inputs:
command: 'test'
Even in microsoft documentation page, they use the DotNetCoreCLI task.

Answer 2

If the vstest task can run successfully on your classic pipeline. It should be working in yaml pipeline too. You can check the agent pool selection and the task's settings to make sure they are same both in yaml and classic pipeline.
1,Your Unit tests seem like running on Vs2017 in the yaml pipeline. You can try running the pipeline on windows-latest agent to run the tests on Vs2019.
If your pipeline has to run on specific agent. You can use VisualStudioTestPlatformInstaller task to download the latest version. Then set the vsTestVersion: toolsInstaller for Vstest task. See below:
- task: VisualStudioTestPlatformInstaller#1
- task: VSTest#2
displayName: 'Test'
inputs:
testAssemblyVer2: '**\bin\**\Tests.dll'
...
...
vsTestVersion: toolsInstaller
2,You can also check out the solution in this thread. As it mentioned in the solution deleting the entire solution folder, re-cloning the project. If you were running your pipeline on your self-hosted agent. You can try using Checkout in the yaml pipeline to clean the source folder before cloning your repo. See below:
steps:
- checkout: self
clean: true
You can also try adding below to your codecoverage.runsettings file under element <CodeCoverage> to exclude the microsoft assemblies as mentioned in the thread.
<ModulePath>.*microsoft\.codeanalysis\.csharp\.dll$</ModulePath>
<ModulePath>.*microsoft\.codeanalysis\.csharp\.workspaces\.dll$</ModulePath>
<ModulePath>.*microsoft\.codeanalysis\.dll$</ModulePath>
<ModulePath>.*microsoft\.codeanalysis\.workspaces\.dll$</ModulePath>
3,You can also try updating 'Microsoft.NET.Test.Sdk' to latest version for test projects.