Do Extension Methods Hide Dependencies?

Question

All,

Wanted to get a few thoughts on this. Lately I am becoming more and more of a subscriber of \"purist\" DI/IOC principles when designing/developing. Part of thi

Answer 1

I think it's fine - because it's not like TruncateToSize is a realistically replaceable component. It's a method which will only ever need to do a single thing.

You don't need to be able to mock out everything - just services which either disrupt unit testing (file access etc) or ones which you want to test in terms of genuine dependencies. If you were using it to perform authentication or something like that, it would be a very different matter... but just doing a straight string operation which has absolutely no configurability, different implementation options etc - there's no point in viewing that as a dependency in the normal sense.

To put it another way: if TruncateToSize were a genuine member of String, would you even think twice about using it? Do you try to mock out integer arithmetic as well, introducing IInt32Adder etc? Of course not. This is just the same, it's only that you happen to be supplying the implementation. Unit test the heck out of TruncateToSize and don't worry about it.