[MTP] Result files not added to results directory

[cbersch]

Describe the bug

Result files added with TestContext.AddResultFile are not saved in the results directory and are referenced by an absolute path when running with MTP.

Using

• .NET 10 RC 2
• MSTest version 4.0.1
• Microsoft.Testing.Extensions.TrxReport version 2.0.1

Steps To Reproduce

1. Use project from mtp_attachment.zip
2. Run with dotnet test --project .\MyProject.csproj -p:UseMtp=true --results-directory=Foobar --report-trx

Expected behavior

• Result files are copied to results directory Foobar.
• Results directory is self-contained.

Actual behavior

Output:

Running tests from bin\Debug\net10.0\MyProject.dll (net10.0|x64)
bin\Debug\net10.0\MyProject.dll (net10.0|x64) passed (346ms)

  In process file artifacts produced:
    - For test 'TestMethod': bin\Debug\net10.0\TestOutput.txt
    - Foobar\somesecretstuff_2025-10-22_10_55_59.8701947.trx

Test run summary: Passed!
  total: 1
  failed: 0
  succeeded: 1
  skipped: 0
  duration: 928ms

And the trx file contains

<ResultFiles>
    <ResultFile path="C:\Temp\mtp_attachment\bin\Debug\net10.0\TestOutput.txt" />
</ResultFiles>

[Evangelink]

I think it would make sense but I would not consider this as a bug as the feature is matching behavior of VSTest per my local test.

[cbersch]

I think it would make sense but I would not consider this as a bug as the feature is matching behavior of VSTest per my local test.

How do you run VSTest? Like I described in the issue?

With .NET 9 and non-MTP execution the attachments are available in the results directory, with MTP they are not.

[Evangelink]

With VSTest, and your example, I see in FooBar:

• amauryleve_ZBOOK-AMAURY_2025-12-10_16_42_01.trx
• amauryleve_ZBOOK-AMAURY_2025-12-10_16_42_01\In\71027058-ba6c-4198-a1cf-6cb455432945\ZBOOK-AMAURY\TestOutput.txt

and the trx has <ResultFile path="ZBOOK-AMAURY\TestOutput.txt" />

which would not match the actual saved path.

If you are seeing something else, please share some screenshot.

[cbersch]

With VSTest, and your example, I see in FooBar:

* `amauryleve_ZBOOK-AMAURY_2025-12-10_16_42_01.trx`

* `amauryleve_ZBOOK-AMAURY_2025-12-10_16_42_01\In\71027058-ba6c-4198-a1cf-6cb455432945\ZBOOK-AMAURY\TestOutput.txt`

and the trx has <ResultFile path="ZBOOK-AMAURY\TestOutput.txt" />

which would not match the actual saved path.

Correct, it doesn't match the actual saved path, but is still contained within the given results directory.

For MTP, the attachment is not saved anywhere in the results directory, but kept in the build directory:

So, copying the results directory to a different machine wouldn't contain all information.

[Mertsch]

This is especially problematic during Azure DevOps build, as each file generates two warnings.

##[warning]File at C:\Build\_work\_temp\Deploy_BuildAgent 20260105T142914_12416\XXX.pdf was not found
Failed to upload result logs to LogStore, Trying to upload to FileService
##[warning]Skipping attachment as it is not available on disk: C:\Build\_work\_temp\Deploy_BuildAgent 20260105T142914_12416\XXX.pdf.

This makes finding actual build warning close to impossible.

[Youssef1313]

It looks like the VSTest behavior here is very specific to TRX. Taking a quick look, it's around this:

https://github.com/microsoft/vstest/blob/7c5988fc7bc814a8ef3b2a39b397f45a71d299fc/src/Microsoft.TestPlatform.Extensions.TrxLogger/Utility/Converter.cs#L437-L541

We might want to replicate the behavior in MTP TRX for parity.