Isolate DiagnosticsTest by disabling its prallelization

[rokonec]

Fixing: System.Net.Http.Functional.Tests timeouts #115683

Context

Functional tests were starting to intermittently hang.
After analyzing I found that just-running diagnostics tests are causing inserting ActivityRecorder test listener which is failing on some verification by Assert.Same. Some of our test expect that sending request by client part of the client <-> server communication will always succeed and hang on server part accepting incoming request.

Changes made

Since Diagnostics tests use process wide telemetry configuration, which is reverted after test runs, I decided to isolate diagnostic tests which leverage ActivityRecorder from other tests by applying [Collection(nameof(DisableParallelization))] to do its job.

Testing

I was able to consistently reproduce this error by running tests in loop. After changes I am no longer able to repro it.

Note

I noticed that after this changes previously detected intermittent test failures also disappeared.

[Copilot]

Pull Request Overview

Isolate DiagnosticsTest by disabling test parallelization to prevent intermittent hangs caused by shared telemetry configuration.

• Added [Collection(nameof(DisableParallelization))] attribute to the DiagnosticsTest base class.
• Introduced using Xunit.Sdk; import.

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[MihaZupan]

#116741 is adding RemoteExecutor to the one test using ActivityRecorder which wasn't already using it. Can you repro the hangs with that change?

[rokonec]

#116741 is adding RemoteExecutor to the one test using ActivityRecorder which wasn't already using it. Can you repro the hangs with that change?

I am trying to repro it with that PR branch.

I found three tests which might be causing is, that PR address only one, and even if other are not causing it by its internal implementation, leaving it as is would make it too fragile for future changes.

Diagnostic tests seems to properly cleanup after each run, which makes me believe we can achieve proper isolation by disabling concurrent running. I prefer this to RemoteExecutor because it is much easier to debug and maybe faster to run.

[rokonec]

Converting to draft for now as it seems that #116741 will address it.

[rokonec]

Seems to be solved by other PR