[Ruby] Testing Models in Rails

[Aaron Patterson]

On Thu, Jul 26, 2007 at 11:41:33PM -0700, Eric Hodel wrote:
> On Jul 26, 2007, at 10:19, Aaron Patterson wrote:
> > On Thu, Jul 26, 2007 at 01:33:31PM -0700, Laurel Fan wrote:
> >> On 7/26/07, Aaron Patterson <aaron at tenderlovemaking.com> wrote:
> >>> This seems like it should be easy, but I can't figure it out!  I  
> >>> have a
> >>> model that defines a before_update callback, and I want to assert  
> >>> that
> >>> that callback is set.  But I don't want to save the object  
> >>> because I'm
> >>> trying to avoid hitting the database.
> >>
> >> Why are you trying to avoid hitting the database?  I would imagine
> >> that avoiding the database makes it hard to test much of anything.
> >
> > Because hitting the database is expensive.  Actually I've found that
> > I can test most of my code without hitting the database.  It makes my
> > tests much faster.  The problem here is that I don't know how to  
> > assert
> > that my callback is defined *without* hitting the database.
> >
> > I trust that the active record callback chain works properly when I  
> > call
> > save.  I just want to make sure that my callback is in that chain.
> 
> I looked into how its stored, and its beyond me.  Maybe you can  
> figure something out.
> 
> User.inheritable_attributes[:before_update] seems to record something  
> related to before_update.

This is what I've got so far:

  def assert_callback(model_class, callback, method_name, message=nil)
    assert(
      (vars = model_class\
        .instance_variable_get(:@inheritable_attributes)).key?(callback) &&
      vars[callback].include?(method_name), message)
  end

Its not perfect, but you can say:

  assert_callback(Model, :before_save, :something)

-- 
Aaron Patterson
http://tenderlovemaking.com/