Treat null and empty as same "state"

[ITaluone]

Hi

I want to test the correct mapping from a DTO to the "real" object.

Now I have following situation:
A property (byte[]) (which is null in the DTO) is mapped as byte[0] in the real object. This causes the test to fail, because null is not empty.

As I read, this behavior is expected from AutoMapper. But unfortunatley I can not override the config.

Is it possible somehow to treat this byte[0] and null as the "same"? (Yes.. I know empty is completely different than null)

expected.Should().BeEquivalentTo(actual, options => options
    .ExcludingMissingMembers()
    .WithAutoConversion()
);

The fail message:
Expected property expected.Image to be <null>, but found {empty}.

[dennisdoomen]

Have you tried https://fluentassertions.com/objectgraphs/#equivalency-comparison-behavior?

[jnyrup]

Here's an example using the linked documentation, which considers null and empty byte[] to be equivalent.

var subject = new { Value = (byte)null };
var expected = new { Value = new byte[0] };

subject.Should().BeEquivalentTo(expected, opt => opt
    .Using<byte[]>(ctx =>
    {
        if (ctx.Subject is null or { Length: 0 } && ctx.Expectation is null or { Length: 0 })
        {
            return;
        }

        ctx.Subject.Should().BeEquivalentTo(ctx.Expectation);
    })
    .WhenTypeIs<byte[]>()
);

[ITaluone]

This was very helpful 👍

Thank you both for your great support!

Just realized you could not have multiple answers as accepted answer. Please feel like I have marked both :)

[rklec]

Note if you want it to be compared for many types, you may go with a solution like this: #1863