Unit Testing a custom attribute class

I have a custom attribute that is just used to mark a member (no constructor, no properties):

[AttributeUsage(AttributeTargets.Property | AttributeTargets.Field, AllowMultiple = false, Inherited = true)]
public sealed class MyCustomAttribute : Attribute { }

How would I unit test this? And, to clarify... I know the 'what', but not the 'how'

I assume there is a way to unit test it to ensure the proper AttributeUsage is in place? So how could I do this? Every time I create a mock class and try to add the attribute to the wrong thing it won't let me compile, so how can I create a bad mock class to test?