Allow tests that return a ValueTask to be discovered

[radmorecameron]

Summary

When using DataTestMethod and DataRow, sometimes only some of the tests will be asyncronous. It'd be nice if test methods that return ValueTask instead of Task or Void can be discovered.

This would be useful if the tests sometime run an async method to get data to pass to it or if the awaited methods in a test are all ValueTask

Here's some example code of when this might be useful :

Example Code

using Microsoft.VisualStudio.TestTools.UnitTesting;
using System;
using System.Diagnostics.CodeAnalysis;
using System.IO;
using System.Threading.Tasks;

namespace TestProject1
{

    [TestClass]
    public class UnitTest1
    {
        public static class Uploader
        {
            // Uploads data or returns false if data is missing
            public static bool Upload(MyFileObject mfo)
            {
                return !(mfo.Data == null || mfo.Data.Length == 0) && mfo.FileName == "Report.pdf";
            }
        }

        public class MyFileObject
        {
            public string FileName { get; set; }
            public byte[] Data { get; set; }
        }


        public enum FileUploadValues
        {
            FileIsUploaded,
            FileBytesIsNull,
            FileBytesIsEmpty,
        }

        [ExcludeFromCodeCoverage]
        [DataTestMethod]
        [DataRow(FileUploadValues.FileIsUploaded)]
        [DataRow(FileUploadValues.FileBytesIsNull)]
        [DataRow(FileUploadValues.FileBytesIsEmpty)]
        public async ValueTask Early_Return_Tests(FileUploadValues fileUploadValue)
        {
            byte[] fileBytes = null;
            if (fileUploadValue == FileUploadValues.FileIsUploaded)
            {
                using (var ms = new MemoryStream())
                {
                    using (var fs = File.Open("./myfile.txt", FileMode.Open, FileAccess.Read, FileShare.Read))
                    {
                        await fs.CopyToAsync(ms);
                        fileBytes = ms.ToArray();
                    }
                }
            }
            else if (fileUploadValue == FileUploadValues.FileBytesIsEmpty)
            {
                fileBytes = Array.Empty<byte>();
            }

            var fileObj = new MyFileObject
            {
                Data = fileBytes,
                FileName = "INVALID_FILE_NAME"
            };

            bool isSuccessful = Uploader.Upload(fileObj);

            Assert.IsFalse(isSuccessful);
        }
    }
}

AB#2300885

[Youssef1313]

@radmorecameron Thanks for reporting this. What TargetFramework are you using for the test project? Also what version are you using?

The support for this should be in 3.5 brought by #3137. However, I can see this is broken if you are using .NET Framework (getting ValueTask via System.Threading.Tasks.Extensions), or if you are using the EOL netcoreapp3.1.

[radmorecameron]

Hi, I am using MSTest 3.6.1 (The metapackage, https://www.nuget.org/packages/MSTest ). This Test project is targeting .NET Framework 4.8 so I guess that's why it's not working. I wrote the example code with .NET 8 (which is working after cleaning and building), sorry for any confusion.