Custom Collector does not emit Console.WriteLine to console

[mide1234]

Description

When running dotnet test with --collect CustomCollector Console.WriteLine is not emitted into the console. Is it intended by design or can it be considered as a bug?

Steps to reproduce

1. Create a custom collector like the following:

    [DataCollectorFriendlyName("SampleDataCollector")]
    [DataCollectorTypeUri("my://sample/datacollector")]
    public class SampleDataCollector: DataCollector
    {
        public override void Initialize(
            System.Xml.XmlElement configurationElement,
            DataCollectionEvents events,
            DataCollectionSink dataSink,
            DataCollectionLogger logger,
            DataCollectionEnvironmentContext environmentContext)
        {
            events.TestCaseEnd += this.Events_TestCaseEnd;
        }

        private void Events_TestCaseEnd(object sender, TestCaseEndEventArgs e)
        {            
            Console.WriteLine("Hello world!");
        }
    }

2. Place it in a new project (the assembly name must end with "collector")
3. Reference this collector project in some test project
4. in console run dotnet test TestProjectFolder --collect SampleDataCollector
5. check there is no sign of "Hello world!" in the console

Expected behavior

Console.WriteLine is emitted to the console.

Actual behavior

Console.WriteLine is NOT emitted to the console.

Environment

Windows 10, netstandard2.0, netcore3.1

[mide1234]

Also note that using the DataCollectionLogger is not much helpful as it offers only logging an error or a warning. In my case it is more about logging a progress. Anyway the logger does not emit the message immediately but it seems to be kept by some dotnet test buffer which is emited to the console at the very end of dotnet test command.

I believe it would be nice to have the option to print some message immediately..

[nohwnd]

This is by design.