Several things I learned this week: 9 Jan

0-INDEX.md

1. Trollop command-line parser lets you parse any array of tokens, not just ARGV. (todoer)
   1b. Bonus: how to have "plug in" options using Trollop
2. When refactoring, it's often tricky to know where a particular set of changes are going to go. So it pays to look in detail at the code beforehand and not jump into writing specs when you don't even know the subject of the tests yet. But in looking at the code, it doesn't mean you're going in to make changes to it.
3. You want to run several implementations, with a different set of fixtures, through the same set of specs. One way. (todoer)

1.rb

# Trollop command-line parser lets you parse any array of tokens, not just ARGV.

opts = Trollop.options( Shellwords.split(str) ) do
   #...
end

# and assuming you _don't_ want to exit, display help, etc. in such cases (you're not at the top level of your app):

p = Trollop::Parser.new do
  #...
end
opts = p.parse(Shellwords.split(str))

1b.rb

# Bonus: how to have "plug in" options using Trollop

# where 'Plugin' is a module that provides the implementation of a given CLI option
# and has module-level accessors for :option_name, :option_desc, :option_type
plugins = [ PluginA, PluginB, PluginC ]

# parse the command line
opts = Trollop.options do
  plugins.each do |plugin|
    opt plugin.option_name, plugin.option_desc, :type => plugin.option_type
  end
end

# get the command class
cmd = CLI::Commands.get(ARGV.shift)

# attach the plugin classes
cmd.extend *plugins

# and run command with the options
cmd.run(opts)

3.rb

# You want to run several implementations, with a different set of fixtures, through the same set of specs. One way.

### test_my_adapter.rb

module Fixtures
  
  def self.adapter_class
    Adapters::MyAdapter
  end
  
  SIMPLE  = #... concrete fixture/dummy/stub for simple case
  COMPLEX = #... etc.
 
end

# run generic tests
require File.expand_path('test_adapter_generic',File.dirname(__FILE__))


### test_adapter_generic.rb

require 'minitest/spec'
MiniTest::Unit.autorun

module Fixtures
  
  # for example - whatever variables you want to test for each input case
  Expectation = Struct.new(:count, :categories, :names)
  
  # the concrete fixtures have to be set up to match these specs
  Expectations = {
    'SIMPLE' =>  Expectation.new( 6, %w(1 2 3 4 5 6), %w(a b c d e f) ),
    'COMPLEX' => Expectation.new #...
   }
  
end

describe 'Adapter#method' do

  def self.get_fixture(fixname)
    unless fix = Fixtures.const_get(fixname) rescue nil
      warn "Note: Fixture not found: '#{fixname}', skipping tests"
    end
    fix
  end

  Fixtures::Expectations.each do |(fixname, expects)|
    
    next unless fix = get_fixture(fixname)
    
    describe fixname do
    
      before do
        # or however the fixture gets injected into the adapter
        @subject = Fixtures.adapter_class.new(fix)  
      end
          
      # for example, showing how the expectations above are used
      it 'must return expected count' do
        assert_equal expects.count, @subject.count
      end

    end

  end

end