hold_the_chocolate.rb

#!/usr/bin/env ruby

# Automatically convert most of the syntax differences between Mocha and RSpec
# Mocks.
#
# Does not handle:
#   - Multiline statements like `Foo\n.expects`
#   - `with` being given a block
#   - Probably other things
#
# You should also check your new uses of `double` for places you could use
# `instance_double` to get protection against stubbing nonexistant methods.

files = Dir[File.join('spec', '**', '*')].select {|file| File.file?(file)}

CONVERSIONS = {
  /(?<=\b)(\S*)\.stubs(?=\()/   => 'allow(\\1).to receive',
  /(?<=\b)(\S*)\.expects(?=\()/ => 'expect(\\1).to receive',
  /(?<=\.)returns(?=\()/        => 'and_return',
  /(?<=\.)raises(?=\()/         => 'and_raise',
  /(?<=\b)stub(?=\()/           => 'double'
}

files.each do |file|
  contents = File.read(file)
  CONVERSIONS.each do |regexp, replacement|
    contents.gsub!(regexp, replacement)
  end
  File.open(file, 'w') { |f| f.puts contents }
end