Rewrite tests from def test_ to test "" and setup/teardown blocks

rewriter.rb

require 'parser/current'
require 'byebug'

class FixDefTest < Parser::Rewriter
  def on_def(node)
    name, args_node, body_node = *node
    if name.to_s.start_with?("test_")
      replace(node.location.keyword, "test")
      replace(node.location.name, %("#{name.to_s.gsub(/^test_/, "").gsub("_", " ")}" do))
    end

    if name == :setup
      replace(node.location.keyword, "setup")
      replace(node.location.name, "do")
    end

    if name == :teardown
      replace(node.location.keyword, "teardown")
      replace(node.location.name, "do")
    end
  end
end

ARGV.each do |file|
  if File.exists?(file)
    code = File.read(file)

    buffer        = Parser::Source::Buffer.new('(example)')
    buffer.source = code

    parser        = Parser::CurrentRuby.new
    ast           = parser.parse(buffer)

    rewriter      = FixDefTest.new

    # Rewrite the AST, returns a String with the new form.
    File.open(file, "w") { |f| f.write(rewriter.rewrite(buffer, ast)) }
  else
    puts "Skipping `#{file}`, not a file"
  end
end