code-challenge.rb

#!/usr/bin/env ruby

# Usage:
# $ ruby code-challenge.rb <github.com repo>
repo = ARGV[0]

# Clear previous challenge
puts "Removing previous directories"
`rm -rf coding-challenge-source`
`rm -rf coding-challenge`

# Clone the candidate's repo
puts "Cloning candidate's challenge repo"
`git clone #{repo} coding-challenge-source`

# Source the Ruby version of the candidate's Rails app
puts "Getting Ruby version"
ruby_version = `cat coding-challenge-source/Gemfile | egrep -o "^ruby ['\\"]([0-9.]+)['\\"]" | egrep -o "[0-9.]+"`

# Ensure that Ruby version is installed locally w/ RVM
puts "Installing Ruby version: #{ruby_version}"
`rvm install #{ruby_version}`
`gem install bundler`

# Install the gems for the candidate's Rails app
puts "Bundling source app"
rails_version = `cd coding-challenge-source && bundle`

# Source the Rails version the candidate has chosen
puts "Getting Rails version"
rails_version = `cd coding-challenge-source && rails -v`[/[0-9.]+/]

# Use that version of Rails to create a new, blank slate Rails application with
# defaults. The -T flag has been used to not install the default Rails test
# framework. This way the candidate's decision to use RSpec or the default
# framework is obvious. It is also made obvious, if the candidate has chosen
# RSpec, whether they are aware of and/or used the -T flag to avoid adding the
# unnecessary default test framework.
puts "Creating new Rails #{rails_version} app (rails _#{rails_version}_ new coding-challenge -T)"
`rails _#{rails_version}_ new coding-challenge -T`

# Commit the newly generated Rails app. Now we can do a diff between two commits
# to see all the code that the candidate contributed.
puts "Adding initial commit after 'rails new'"
`cd coding-challenge && git init . && git add . && git commit -m 'Initial commit'`

# Move the candidate's code into the project directory, recursively overwriting
# any files generated by the `rails new` command a few steps back.
puts "Copying files from candidate's challenge into new Rails app"
`cp -r coding-challenge-source/* coding-challenge`

# Add a commit to allow `git log` to show the difference between the default
# `rails new` output and the candidate's contribution.
username = repo[/github.com\/(.+)?\//, 1]
puts "Adding and committing candidate's code"
`cd coding-challenge && git add . && git commit -m '#{username} code submission'`

# Clean up the temporary folder created earlier.
puts "Removing temporary directory"
`rm -rf coding-challenge-source`