false-positive xUnit1039 errors for tuples with mismatching member names.

[BrunoJuchli]

When using tuples as test-method input and the tuple member names don't match, MemberDataShouldReferenceValidMember generates type-mismatch errors like:

error xUnit1039: The type argument (System.DateTime a, System.DateTime b) from TestClass.Data is not compatible with the type of the corresponding test method parameter _

I consider this a false-positive because even when the member names don't match, the tests will still run correctly.

If the current behavior is deemed as desired, I would however recommend to improve the error message. Ideally the message could tell me, that the type matches but the tuple member names don't.

Examples

TheoryData<> does not define names for tuple members, but Test methods does

.. or vice versa.

using System.Collections.Generic;
using Xunit;

public class TestClass {
    public static TheoryData<(int, int)> Data;

    [MemberData(nameof(Data))]
    public void TestMethod((int a, int b) _) { }
}

TheoryData<> defines a different name than test method

using System.Collections.Generic;
using Xunit;

public class TestClass {
    public static TheoryData<(int a, int b)> Data;

    [MemberData(nameof(Data))]
    public void TestMethod((int a, int iUseAnotherNameHereWhichIMakeExtraLongToBeObvoius) _) { }
}

This Works

When the tuple member names match, there's no error:

using System.Collections.Generic;
using Xunit;

public class TestClass {
    public static TheoryData<(int a, int b)> Data;

    [MemberData(nameof(Data))]
    public void TestMethod((int a, int b) _) { }
}

[JamesTerwilliger]

On it

[JamesTerwilliger]

@bradwilson xunit/xunit.analyzers#179

[bradwilson]

Available in 1.11.0-pre.6 https://xunit.net/docs/using-ci-builds