How do check class should be with internal modifier?

[BenMorris]

AreNotPublic() is your friend here, i.e. this code snippet from the unit tests

            var result = Types
                .InAssembly(Assembly.GetAssembly(typeof(ClassA1)))
                .That()
                .ResideInNamespace("NetArchTest.TestStructure.Scope")
                .And()
                .AreNotPublic().GetTypes();

Returns the InternalClass type.