Fixtures with No Underlying DB

Why are you using AR?  Could you not just use a plain ole ruby object?  hehe, PORO (sorry, java joke).

It seems like this "non-inserted" fixture use-case is one of the less universal, but still rather common, requirement in testing.  It would be nice if there were some convention in Rails to handle it.  Either some annotation in YAML that would cause the fixture to be instatiated, but not inserted or some supplementary file fixtures/<model>_nonDB.yaml, etc.

Both model and controller tests tend to want to have a "stock" good but not inserted fixture to work with to test the successful paths, as well as allowing for programmatic mutations to create known failing cases.

I don't agree.  Active Record is an Object Relational Mapping tool.  Changing it to support anything else would add unecessary complication to the code base.  For example, how would you handle "validates_uniqueness_of"?  It breaks the whole paradigm. 

It would be cool to be able to load fixtures into non AR objects, and I'm sure there's a way to do it.  But using Active Record without a database, and loading fixtures into a sans db AR object just seems like asking for trouble.

Both sides have a lot of merit here... 

vin's point about the "simplest thing that works" is very important -- however in Rails, leveraging AR for a lot of non-DB tasks is seen by some as the simplest thing and thus there is the constant push of the square peg into a round hole.

Now given Ruby's flexible nature, I suspect it should be possible to mixin some of the validation and object creation methods into a non-AR class and thus have a validateable class that doesn't expect the rest of the AR infrastructure.  (Some validations, such as uniqueness_of, as mentioned above don't make sense across such a mixin, though)

If the validation aspect is hard to seperate from the AR aspect, it might be worth talking to core about possible refactorings that would be acceptible to them to make the validations more re-useable outside the context of an AR.

(This doesn't directly address the non-inserted fixture topic, which has uses even when a "normal" AR is being used.)

What vin is saying is that using "Clients change their minds and say, "would you mind storing that information"?" as one of your reasons for using AR without a database is premature.  IMO, too many developers, including myself say, "well what if the client asks for this?".  Certainly there are sometimes where it makes sense.  However, if you're fairly certain they're going to ask for it, why not just do it?  Otherwise it can always wait.