I had some Ruby code that utilized File::SEPARATOR and File::PATH_SEPARATOR to run on both unix and windows, so I wanted to stub these values to test for both platforms. There are couple examples out there, building on each other. This example adds a feature that saves and recalls the former value and this example builds on that to support class constants. Both expect Activerecord, so there’s a little working around that added here. I’m ripping this directly from my spec_helper.rb before I throw it away because it feels over-engineered and complicated.

def with_warnings(flag)
  old_verbose, $VERBOSE = $VERBOSE, flag
  yield
ensure
  $VERBOSE = old_verbose
end

# http://missingbit.blogspot.com/2011/07/stubbing-constants-in-rspec_20.html
def parse_constant(constant)
  source, _, constant_name = constant.to_s.rpartition('::')

  [constantize(source), constant_name]
end

def with_constants(constants, &block)
  saved_constants = {}
  constants.each do |constant, val|
    source_object, const_name = parse_constant(constant)

    saved_constants[constant] = source_object.const_get(const_name)
    with_warnings(nil) {source_object.const_set(const_name, val) }
  end

  begin
    block.call
  ensure
    constants.each do |constant, val|
      source_object, const_name = parse_constant(constant)

      with_warnings(nil) { source_object.const_set(const_name, saved_constants[constant]) }
    end
  end
end
####################

# File activesupport/lib/active_support/inflector/methods.rb, line 209
def constantize(camel_cased_word)
  names = camel_cased_word.split('::')
  names.shift if names.empty? || names.first.empty?

  constant = Object
  names.each do |name|
    constant = constant.const_defined?(name) ? constant.const_get(name) : constant.const_missing(name)
  end
  constant
end

Then you can perform:

  it "does something when running on Windows" do
    with_constants "::File::PATH_SEPARATOR" => ";" do
      # code
    end
  end

I had a need to grab all of the Github repositories for Cookbooks, which is a Github user maintained by the Chef community for collecting many cookbooks in one place for development. All of these cookbooks should be on the Opscode Community site, which is where you should go if you’re browsing for cookbooks to use yourself. But I needed to grep through a large number of cookbooks to develop statistics on Chef Cookbook usage patterns, so I needed All The Things.

#!/usr/bin/env ruby
# 2012-01-11 Bryan McLellan <btm@loftninjas.org>
# Fetch the list of repositories from a Github user and 'git clone' them all

require 'rubygems'
require 'json'
require 'net/http'

url = "http://github.com/api/v2/json/repos/show/cookbooks"
dir = "cookbooks"

if File.basename(Dir.getwd) != dir
 if File.exists?(dir)
   puts "Target directory of '#{dir}' already exists."
   exit 1
 end

 Dir.mkdir(dir)
 Dir.chdir(dir)
end

resp = Net::HTTP.get_response(URI.parse(url))
data = resp.body

result = JSON.parse(data)

result['repositories'].each { |repo|
 puts "Fetching #{repo['url']}"
 system "git clone #{repo['url']}"
}