MethodDataSource expects ValueTuple on 8 arguments

[dev-in-disguise]

Hi Thom!
I'm having the following test that uses MethodDataSource which points to a method that returns a tuple of the values I'm expecting as arguments.

[Test]
[MethodDataSource(nameof(T5_DeconstructTestDataSource))]
public async Task T5_Deconstruct_Should_ReturnAllResults(bool expectedSuccess, string? expectedError,
    string? expectedT0, string? expectedT1, string? expectedT2, string? expectedT3, string? expectedT4, string? expectedT5)
{
    
}

public static
    IEnumerable<(bool success, string? expectedError, string? expectedT0, string? expectedT1, string? expectedT2,
        string? expectedT3, string? expectedT4, string? expectedT5)>
    T5_DeconstructTestDataSource()
{
    yield return (true, null, "This is a success", null, null, null, null, null);
    yield return (false, "This is a failure", null, null, null, null, null, null);
}

This leads to the following error (plus 3 additional ones for the generated test code from TUnit that basically tell the same thing):

TUnit0001: Attribute argument types 'bool, string?, string?, string?, string?, string?, string?, System. ValueTuple<string?>' don't match method parameter types 'bool, string?, string?, string?, string?, string?, string?, string?'

Why is there suddenly a ValueTuple<string?> assumed by TUnit? Is there a hard limit for how many types TUnit supports?

By the way if I add further arguments to my test method and the data source they get then added to the ValueTuple.

Of course I could create an own type for the test data but still it would be great if this edge case could be either documented or a fix for it discovered.

Thank you so much Thom in case you get once again to a solution!

[thomhurst]

Hey @dev-in-disguise,

This is a weird one indeed. Looks like Roslyn is giving me the wrong types when inspecting them!?

I've raised an issue with them: dotnet/roslyn#76714