From: obscured by code <javierg1975@...>
Date: 2005-11-01T07:27:12+09:00
Subject: Re: <ANN> TeSLa, a Domain Specific Language for Unit Testing

No part of the code makes that line true, that line is a precondition
to the success of the assert once the method is run. That is,
  requires {@items = [:item1, :item2, :item3]}
is executed *before*
  add_item => [:item4]
Look at it as initialization code if you like. In other words, it is
*required* for the 'items' property to hold items 1 to 3 so the
addition of a fourth one would  make the
  assert {size == 4}
line true.
Below is the entire Catalog class from example.rb. Perhaps that would
help make things clearer

class ShoppingCart

	def add_item item
		@items << item
 	end

	def size
		@items.length
	end

	attr_accessor :items

	test_method :add_item => [:item5] do

		# requires makes sure certain conditions are met before the
                # assert is run

		requires {@items = [:item1, :item2, :item3]}
		assert {size == 4}	
	end
	
end