$ ruby PissTest.rb
Loaded suite PissTest
Started
E
Finished in 0.000399 seconds.

  1) Error:
test_0001_stink_test_(PoopkitSpec):
NoMethodError: undefined method `vns' for PoopKit::Stink:Class
    /home/me/lib/Poop.rb:14:in `a2s'
    PissTest.rb:10:in `block (2 levels) in <main>'

1 tests, 0 assertions, 0 failures, 1 errors, 0 skips

Test run options: --seed 54082
--snip--
Poop.rb is as follows:
#2345678901234567890123456789012345678901234567890123456789012345678901234567890
module PoopKit

    require 'lib/Piss.rb'

    include Piss

    class BClass
    end

    class Stink < BClass

        def self.a2s(myStr)
            lstr = vns(myStr,'desc')
        end

    end

end
--snip--
Piss.rb is as follows:

   #   Upper Level Classes Only

module Piss

    def vns(sU,mStr)
        # Note:  This method validates, AND returns a stripped value.  That is its intent.

        # Unless the argument is a String, it fails validation

        unless sU and sU.class == String
            raise ArgumentError, "Invalid #{self.class} sU argument '#{sU}' in #{mStr} method."
        end

        return sU
    end

end
--snip--
Then test/PissTest.rb is as follows:

require 'lib/Poop'
require 'minitest/spec'
require 'minitest/autorun'

describe PoopKit do

    include PoopKit

    it "Stink test:" do
        Stink.a2s("http://hostname:80").must_equal 'hostname:80'
    end

end
--snip--