NUnit runner fails when test method returns ValueTask<>

[toolmagic]

Versions:

Nuget packages:
NUnit 3.10.1
NUnit3TestAdapter 3.10.0
System.Threading.Tasks.Extensions 4.5.1

Environment:
Windows 10.1803 17134.286
Visual Studio 2017 15.8.4

Steps to Reproduce:

1. Create C# Class Library, .NET 4.7.2
2. Add Nuget references for NUnit, NUnit3TestAdapter and System.Threading.Tasks.Extensions
3. Add Test Class:

using System.Threading.Tasks;
using NUnit.Framework;

namespace ClassLibrary1
{
    public class Class1
    {
        [Test(/*ExpectedResult = 100*/)]
        public async ValueTask<int> AsyncGetValueTest()
        {
            return await Task.FromResult(100);
        }
    }
}

4. Run test "AsyncGetValueTest"

Expected Behavior:
NUnit says "Missed ExpectedResult in Test attribute" or "Test methods with return type ValueTask<> are not supported"

Actual Behavior:
NUnit fails with an internal error:
System.NullReferenceException : Object reference not set to an instance of an object.
at NUnit.Framework.Internal.AsyncInvocationRegion.AsyncTaskInvocationRegion.WaitForPendingOperationsToComplete(Object invocationResult)
at C:\src\nunit\nunit\src\NUnitFramework\framework\Internal\AsyncInvocationRegion.cs:line 109
at NUnit.Framework.Internal.Commands.TestMethodCommand.RunAsyncTestMethod(TestExecutionContext context)
at C:\src\nunit\nunit\src\NUnitFramework\framework\Internal\Commands\TestMethodCommand.cs:line 96

[mikkelbu]

This is related to #2286, but you are right that we at least could give a better exception/warning message instead of a NRE until #2286 is solved.

[toolmagic]

@mikkelbu , exactly. It's better to say "a feature is not supported" until the feature is implemented.

[jnm2]

Fixed in the prerelease feed and included in 3.12 which is just around the corner!