the benefits I see: - nullable (test double/mock) updates would be more natural, easier, since it is located right there in prod code. (One level of indirectio

the benefits I see: - nullable (test double/mock) updates would be more natural, easier, since it is located right there in prod code. (One level of indirection removed) - with authoritative location of test double, it reduces the risk of test double proliferation/duplication (I doubt I will use it in the proposed form though, saving test double code in prod is not for me probably)