ComparingByMembers<object> lets structural equality assertions always succeed

Description

I want to be able to configure FluentAssertions’ structural equality so that it uses ComparingByMembers for all types. The background for this is that I have a mix of F# and C# code and all F# records implement Equals by default. In case of an object-graph with a mix starts using Equals when hitting the first F# record, as well for the nested C# classes.

I tried ComparingByMembers<object>, but that results in the tests always being succeeded. And I guess that should be fixed.

Complete minimal example reproducing the issue

using FluentAssertions;
using Xunit;

namespace CSharp.FluentAssertionWrapper
{
    public class Facts
    {
        public struct C
        {
            public D D { get; set; }
        }
        public class D
        {
            public string S { get; set; }
            public int I { get; set; }
        }

        [Fact]
        public void Foo()
        {
            var a = new C { D = new D { S = "a", I = 17 } };
            var b = new C { D = new D { S = "a", I = 18 } };

            a.Should().BeEquivalentTo(   // this should fail, but succeeds
                b,
                config => config.ComparingByMembers<object>());
        }
    }
}

Expected behavior:

All types are structurally compared correctly.

Actual behavior:

Assertion always succeeds.

Versions

• Which version of Fluent Assertions are you using? 5.10.3
• Which .NET runtime and version are you targeting? netcoreapp3.1

Additional Information

None.

[ursenzler]

I think that would work.

Should I try to contribute that? I probably need some help though. I don’t really understand the code around SelfReferenceEquivalencyAssertionOptions, which is somehow involved in the affected code.

[dennisdoomen]

That’s what I was thinking,e.g. ComparingByMembers(Func<Type, bool> predicate)