Weird issue using spread operator on IEnumerable<Task> when using mocked methods

[sbloomfieldtea]

Describe the Bug

I will preface this by saying I think I may be doing something wrong.

If I have multple task objects returned from mocked async methods stored in the result of a linq query and I use the ".." spread operator, each item in the result gets set to null.

If I have multple task objects returned from "real" async methods stored in the result of a linq query and I use the ".." spread operator, each item is a valid task and is not null.

I assume it has something to do with the linq query and a delay in resolving the enumerable? But then why would it only behave this way when the method is mocked?

Steps to Reproduce

Here's an example unit test. Only the last assert "mockedMethodTasksSpread" fails.

    public class MyTestClass
    {
        [TestMethod]
        public async Task TestTaskSpread()
        {
            var idList = new string?[] { "31", null, "33", "34" };

            var myMock = new Mock<IMyInterface>();
            myMock.SetupSequence(_ => _.MyTestAsync(It.IsAny<string>(), It.IsAny<CancellationToken>()))
                .ReturnsAsync("41")
                .ReturnsAsync("42")
                .ReturnsAsync("43")
                .ReturnsAsync("44");

            var realMethodTasks = idList
                .Where(s => !string.IsNullOrWhiteSpace(s))
                .Select(id => MyRealMethodAsync(id!));

            Task<string?>[] realMethodTasksToArray = realMethodTasks.ToArray();
            Task<string?>[] realMethodTasksSpread = [.. realMethodTasks];

            var mockedMethodTasks = idList
                .Where(s => !string.IsNullOrWhiteSpace(s))
                .Select(id => myMock.Object.MyTestAsync(id!, default));

            Task<string?>[] mockedMethodTasksToArray = mockedMethodTasks.ToArray();
            Task<string?>[] mockedMethodTasksSpread = [.. mockedMethodTasks];

            CollectionAssert.AllItemsAreNotNull(realMethodTasksToArray, "realMethodTasksToArray");
            CollectionAssert.AllItemsAreNotNull(realMethodTasksSpread, "realMethodTasksSpread");

            CollectionAssert.AllItemsAreNotNull(mockedMethodTasksToArray, "mockedMethodTasksToArray");
            CollectionAssert.AllItemsAreNotNull(mockedMethodTasksSpread, "mockedMethodTasksSpread");
        }

        private async Task<string?> MyRealMethodAsync(string id)
        {
            await Task.Delay(10);

            return await Task.FromResult(id);
        }
    }

    public interface IMyInterface
    {
        Task<string?> MyTestAsync(string myString, CancellationToken cancellationToken);
    }    

Expected Behavior

The assert mockedMethodTasksSpread should pass.

Exception with Stack Trace

None

Version Info

Here's most of my csproj with nuget versions:

<Project Sdk="Microsoft.NET.Sdk">
	<PropertyGroup>
		<TargetFramework>net8.0</TargetFramework>
		<ImplicitUsings>enable</ImplicitUsings>
		<Nullable>enable</Nullable>
		<IsPackable>false</IsPackable>
		<Platforms>x64</Platforms>
		<IsTestProject>true</IsTestProject>
	</PropertyGroup>
	<ItemGroup>
		<PackageReference Include="FluentAssertions" Version="6.12.1" />
		<PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.11.1" />
		<PackageReference Include="Moq" Version="4.20.72" />
		<PackageReference Include="MSTest.TestAdapter" Version="3.6.1" />
		<PackageReference Include="MSTest.TestFramework" Version="3.6.1" />
	</ItemGroup>
</Project>

Additional Info

None