From: Robert Klemme <shortcutter@...>
Date: 2009-12-10T16:36:07+09:00
Subject: Re: Chain Method in Class with Method in Module

On 10.12.2009 07:55, Raymond O'Connor wrote:
> Aaron Patterson wrote:
>> On Thu, Dec 10, 2009 at 01:33:58PM +0900, Raymond O'Connor wrote:
>>> I'd like to chain setup in a unit test, so that it calls a method in a
>>> module BEFORE running through the setup code.  I'd like to do it without
>>> having to put super() in the test's setup method.
>> What's wrong with super()?  We use it in all of our other objects.
>> Tests are normal objects too.  :-)
> 
> Trying to keep things as encapsulated as possible.  Just seems wrong 
> that people including the module need to know to call super in setup 
> before their own setup code.

That's the normal way to do business with super classes - and included 
modules.  If you look at MyUnitTest.ancestors you will see that the 
class is first in the chain and *then* the included module appears. 
That's why #setup of your class is always invoked before #setup in any 
included module.

Another solution to what you want to do would be this: use the template 
method pattern.

module InstanceMethods
   def setup
     puts 'module setup'
     setup_local
   end

   def setup_local
     raise "Sub class needs to implement this!"
   end
end

class MyUnitTest < Test::Unit::TestCase
   include InstanceMethods

   def setup_local
     puts 'class setup'
   end
end

Although you can still break the pattern by defining #setup in the class 
because Ruby does not have final methods (e.g. like Java).

Raymond, why do you use two modules here?  As far as I can see there is 
no use case for a second module.  Also, you could make InstanceMethods a 
regular class which inherits Test::Unit::TestCase.  Placing this in a 
module only pays off if you want to include the module in classes which 
need to have differing super classes.

A completely alternative way would be to define a mini DSL where you 
have full control over what happens:

# untested
def test(&b)
   Class.new do
     def setup
       puts 'module setup'
       super
     end
   end.send(:include, Module.new(&b))
end

MyUnitTest = test do
   def setup
     puts 'class setup'
   end
end

Kind regards

	robert

-- 
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