TestAdapter: Wrongly grouped DataTestMethod

Describe the bug

DataTestMethods are wrongly grouped with MSTest.TestAdapter in version 3.0.x (Grouping in VS is by Traits)

Wrong grouping:

Expected grouping (achieved with MSTest.TestAdapter 2.2.x):

Steps To Reproduce

Explore tests in this class:

using Microsoft.VisualStudio.TestTools.UnitTesting;

namespace TestProject
{
    [TestClass]
    [TestCategory("L3")]
    public class BasicUnitTest : UnitTestBase
    {
        public override int TypeCount => 3;
    }
    
    [TestClass]
    [TestCategory("L3")]
    public class ExtendedUnitTest : UnitTestBase
    {
        public override int TypeCount => 8;
    }

    [TestClass]
    [TestCategory("L3")]
    public class UnitTestBase
    {
        public virtual int TypeCount => 5;

        [DataRow(1)]
        [DataRow(2)]
        [DataTestMethod]
        public void DocumentCostCurrentDataFunctions(int count)
        {
            Assert.IsTrue(count < TypeCount);
        }
    }
}

Expected behavior

Expected grouping (achieved with MSTest.TestAdapter 2.2.x):

Actual behavior

Wrong grouping:

Additional context

We also run tests in Azure DevOps wth vstest.console.exe "C:\abc.dll" /TestCaseFilter:"TestCategory=L3" "/logger:trx;LogFileName=C:\abc.trx" /TestAdapterPath:"C:\UnitTests\Tests" command. The test report file has changed after the libraries update.

AB#1813781

[HightowerCZ]

OK, I put the comment to the linked issue. Thank you for being so helpful!

[Evangelink]

Hi @HightowerCZ,

I am waiting for a little more info about the change of behaviour in VS because it’s not yet fully clear if this is coming from a change caused by MSTest or VS Test Explorer. I will let you know more when I have some news.

Regarding the change in the trx, this is not linked to traits grouping but linked to a change of behavior (breaking change) that was introduced in 2.2.4. This is unfortunate but sadly we cannot easily change this on our side because we need to synchronize with Azure DevOps team to ensure the UI will reflect the change. To get more information about this change, I encourage you to refer to https://github.com/microsoft/testfx/issues/1024.