> 1) You move the adding logic to it's own file, with other adding-only responsibilities
The code snippet above says nothing about where the adding logic is, other than that one places it in a method while another uses a straight function. Said method/function can live anywhere, unless you have a specific language in mind that prevents you from moving functions to a file?
> 2) You allow injecting different implementations of Adder - maybe introducing a more efficient one in some cases but not others
The thing the code wants to do is add something, so if that can be made more efficient, it can be made more efficient by implementing a more efficient add function. Why is it that you need to introduce something that is not an add function, in order to inject a more efficient add function? Why can you inject an Adder but not add()? What language is that again?
> 3) You enable mocking Adder so that your logic that verifies that B and C are added can be tested without having to re-add B and C all the time.
This makes no sense to me. If you add B and C, you test it once, so what's the deal with this re-adding? And why can't you mock add()?
The code snippet above says nothing about where the adding logic is, other than that one places it in a method while another uses a straight function. Said method/function can live anywhere, unless you have a specific language in mind that prevents you from moving functions to a file?
> 2) You allow injecting different implementations of Adder - maybe introducing a more efficient one in some cases but not others
The thing the code wants to do is add something, so if that can be made more efficient, it can be made more efficient by implementing a more efficient add function. Why is it that you need to introduce something that is not an add function, in order to inject a more efficient add function? Why can you inject an Adder but not add()? What language is that again?
> 3) You enable mocking Adder so that your logic that verifies that B and C are added can be tested without having to re-add B and C all the time.
This makes no sense to me. If you add B and C, you test it once, so what's the deal with this re-adding? And why can't you mock add()?