def target = Stub(SomeType)
        target.value >> 12

        expect:
        def impl1 = generate(SomeTypeImpl, SpecializedType)
        def impl2 = generate(SomeTypeImpl, SpecializedType2)
        impl1 != impl2
        SpecializedType.isAssignableFrom(impl1)
        SpecializedType2.isAssignableFrom(impl2)
    }