Tests fail to run for UWP projects with Minimum Versions set to RS2 (15063) or earlier - Regressed with TestAdapter 2.2.1

Description

Attempting to run tests for a UWP unit test project with Minimum Version set to RS2 (15063) or earlier fails with an error about not being able to load System.Xml.ReaderWriter. This regressed starting with MSTest.TestAdapter version 2.2.1. It reproes both in and outside of Visual Studio.

Steps to reproduce

1. Create a C# UWP test project. This brings up a wizard where you select two values. You can leave “Target Version” set to the default, but for “Minimum Version” change it to “Windows 10 Creators Update (10.0; Build 15063)”. Anything older will repro the issue as well.
2. Manage NuGet Packages for the project and update the version used for MSTest.TestAdapter to 2.1.2.
3. Build the project and run all tests, it should work fine.
4. Go back to Manage NuGet Packages and update the version used for MSTest.TestAdapter to 2.2.1 or anything newer.
5. Rebuild and run all tests again.

Expected behavior

The test should pass.

Actual behavior

The test fails to run, with the following error listed in the Test pane of the output window:

An exception occurred while invoking executor 'executor://mstestadapter/v2': Could not load file or assembly 'System.Xml.ReaderWriter, Version=4.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)

Environment

• Operating system: Win10, repro’d on various versions between RS5 and 21H1
• Build version of vstest.console: Repro’d with 16.10.0-release-20210520-03 and 16.11.0-release-20210626-04
• Package version of MSTest.TestAdapter: 2.2.1 - 2.2.5

[Evangelink]

After discussion with management we agreed on doing nothing as the issue is quite old and the number of impacted users is quite low.

[Evangelink]

I did some investigation and indeed there were some implicit breaking change done by updating Test Platform. It’s going to be too complex to do any fix on older versions because of all the other changes…

On MSTest v3, I have made it explicit that we are dropping some older target frameworks that are no longer supported (see https://github.com/microsoft/testfx/issues/1274#issue-1383430926).

I will discuss with management to see what options we could provide but I guess the only suitable at the moment is for you to stay on the older version that was still supporting UWP version you want to target.