From: ded <ded-google@...>
Date: 2005-09-04T02:36:26+09:00
Subject: Newbie Q: Self-Testing Ruby Files (Double Assignment to Constants)

I like to make class files self-testing and can do so with the
following arrangement:

==================== Junk.rb ==========================
Class Junk
  CONST = 'a value'
  def initialize
  end
end

# Unit tests
if __FILE__ == $0
    require 'test/TestJunk.rb'
end

===================== test/TestJunk.rb ==================
require 'test/unit'
require 'Junk' unless defined?(CONST)

class TestJunk < Test::Unit::TestCase
    def test_sometest
        assert(<<some assertion>>, "Some message")
    end
end
==========================================================

The thought is that I can run Junk.rb or TestJunk.rb as a top-level
script and have the unit tests run either way.

This works, EXCEPT if I run Junk.rb it complains that I have already
assigned to CONST, so it is apparently loading Junk.rb twice.

I tried to avoid these with the if defined?(CONST) construct, but ot
does not help.

Questions:

1. I thought the 'require' method would load the file only if it was
not loaded already.  If so, how could two requires result in two
executions of the CONST = 'some value' line?  There's something I'm not
getting here.

2. Why doesn't the "if defined?(CONST)" thingy help?  I would think it
is unnecessary given my assumption in 1.  I'm definitely confused.

Ruby-Nuby in need of guidance.

Thanks.