Parallelizable TestFixtureSource with TestFixtureData not running in parallel

[LifshesOfer]

NUnit (targeting .NET 5) does not run my TestFixture in parallel instances when using TestFixtureSource:

public class TestFixtureCases
{
	public static IEnumerable Cases
	{
		get
		{
			yield return new TestFixtureData("string1");
			yield return new TestFixtureData("string2");
			yield return new TestFixtureData("string3");
		}
	}
}
[TestFixture]
[Parallelizable]
[TestFixtureSource(typeof(TestFixtureCases), nameof(TestFixtureCases.Cases))]
public class FixtureClass : BasicFixtureClass
{
	public FixtureClass(string fixtureCase) : base(fixtureCase)
	{ }

	[Test]
	public void test1()
	{ }
	[Test]
	public void test2()
	{ }
}

However, if I'm giving the FixtureCases like the below, it does run in multiple instances:

[TestFixture("string1")]
[TestFixture("string2")]
[TestFixture("string3")]
[Parallelizable]
public class FixtureClass : BasicFixtureClass
{
	public FixtureClass(string fixtureCase) : base(fixtureCase)
	{ }

	[Test]
	public void test1()
	{ }
	[Test]
	public void test2()
	{ }
}

[rprouse]

I am going to mark this as Confirm so that we can determine if this is a .NET 5 problem or a general problem. I expect it is a general problem, but I want to check.

[TrxIsVerCtrl]

@rprouse I have the exact same issue on .NET4.7.1 with NUnit 3.13.1. Is there any chance this being included in next release?

[mcichonqa]

I got it in .NET Core 3.1 also.

[davidoh99]

Also having this issue; using ver 3.12 as a workaround. I'm using .NET 5 and have no problems with 3.12.

[jairbubbles]

I do confirm that using version 3.12 does fix the issue.

[MattNorgren]

Ran into this in 3.13.2, and downgrading to 3.12 fixed the issue. Targeting netcoreapp3.1.

[MattNorgren]

@rprouse Down revving to 3.12 to get around this issue is not a good solution for me.

[CeesKaas]

I've narrowed it down to 247ede8
which seems logical that if you don't add the attributes of a class that it wouldn't be picked up for parallelizable

[agray]

Can the one line in 247ede8 not be added back?

[jairbubbles]

Hey all, I'm proposing a fix for this: #4099