VSLive Vegas 2016: Unit Testing for Mere Mortals Slides & Code

3 responses to “VSLive Vegas 2016: Unit Testing for Mere Mortals Slides & Code”

1. 

   Matt R

   March 11, 2016

   Thanks for sharing Ben! A question on slide 24 (Advertise Dependencies on Constructor):

   What are your thoughts on good/bad design to give the option to inject a dependency, but not force it?

   So, within the constructor, basically combine the “less awesome” and “more awesome” code example:

   public PersonManager(IPersonalRepository instance)
   {
   if (instance == null)
   m_Repository = new SqlPersonRespository();
   else
   m_Repository = instance;
   }

   So, as the calling code, I know the default behavior is to use a SqlPersonRespository (because somebody documented the API…) and I only inject a dependency if I need to change that default behavior (such as for mocking).

   Pros / Cons?

   Thanks,
   Matt

   Reply
2. 

   Matt R

   March 11, 2016

   Actually, if I took that previous comment example one step further, I’d create a constructor overload that didn’t include a parameter. That way, I’m not forcing the consumer to pass a null parameter in the first place…

   Then, as calling code, I could do either:

   var sqlRepo = new PersonManager(); // uses SqlPersonRepository
   var mockRepo = new PersonManager(myMockRepository);
   var oracleRepo = new PersonManager(myOracleRepository);

   Reply
   1. 

      Ben Day

      March 11, 2016

      Hi Matt —

      The option to pass in a null as a parameter feels like you’re inviting bad things to happen. Two thumbs down on that approach.

      I like the “two constructors” version a whole lot better. I actually use this sometimes when I want testability but I don’t feel like taking the dependency on an IoC framework / DI framework. You’ve got a *little* bit of an unadvertised dependency in that class using that approach but if someday you need/want to refactor to remove that dependency, most of the work is already done.

      Honestly, that’s a pretty good design approach.

      -Ben

      Reply

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