Exploring options for library loader (first find a file?)

lib_path.rb

# frozen_string_literal: true
module BuildPath
  def library_path(base, name, ext)
    File.join(base, 'library', name, "#{name}.#{ext}")
  end

  def processing_library_path(base, name, ext)
    File.join(base, name, 'library', "#{name}.#{ext}")
  end
end

# build library paths
class LibPath
  include BuildPath
  K9_ROOT = '/home/tux/.gem/ruby/2.4.0/gems/jruby_art-1.3.1'.freeze
  SKETCHBOOK = '/home/tux/sketchbook3/libraries'.freeze
  SKETCH_PATH = '/home/tux/libpath/test'.freeze
  PROCESSING_ROOT = '/usr/share/processing/modes/java/libraries'.freeze

  def find_library(name)
    message = 'no such file to load -- %s'
    if File.exist?(first = local_ruby(name))
      return first
    end
    if File.exist?(first = installed_ruby(name))
      return first
    end
    if File.exist?(first = local_java(name))
      return first
    end
    if File.exist?(first = installed_java(name))
      return first
    end
    if File.exist?(first = installed_mode(name))
      return first      
    end
    raise(LoadError.new, format(message, name))
  end

  private

  def local_ruby(name)
    library_path(SKETCH_PATH, name, 'rb')
  end

  def local_java(name)
    library_path(SKETCH_PATH, name, 'jar')
  end

  def installed_ruby(name)
    library_path(K9_ROOT, name, 'rb')
  end

  def installed_java(name)
    processing_library_path(SKETCHBOOK, name, 'jar')
  end

  def installed_mode(name)
    processing_library_path(PROCESSING_ROOT, name, 'jar')
  end
end

lib_path_test.rb

# frozen_string_literal: true
require_relative 'test_helper'
require_relative '../lib/lib_path'

# The test class
class TestLibPath < Minitest::Test
  LOCAL_RUBY = '/home/tux/libpath/test/library/local/local.rb'.freeze
  LOCAL_JAVA = '/home/tux/libpath/test/library/local_java/local_java.jar'.freeze
  INSTALLED_RUBY = '/home/tux/.gem/ruby/2.4.0/gems/jruby_art-1.3.1/library/boids/boids.rb'.freeze
  INSTALLED_JAVA = '/home/tux/sketchbook3/libraries/sound/library/sound.jar'.freeze
  PROCESSING_ROOT = '/usr/share/processing/modes/java/libraries/svg/library/svg.jar'.freeze
  attr_reader :first

  def setup
    @first = LibPath.new
  end

  def test_select_mode
    assert_equal PROCESSING_ROOT, first.find_library('svg')
  end

  def test_select_installed_java
    assert_equal INSTALLED_JAVA, first.find_library('sound')
  end

  def test_select_local_java
    assert_equal LOCAL_JAVA, first.find_library('local_java')
  end

  def test_select_installed_ruby
    assert_equal INSTALLED_RUBY, first.find_library('boids')
  end

  def test_select_local_ruby
    assert_equal LOCAL_RUBY, first.find_library('local')
  end

  def test_library_not_found
    assert_raises(LoadError, 'no such file to load -- xxxx') do
      first.find_library('xxxx')
    end
  end
end