doh.rb

require 'coverage'
require 'json'

Coverage.start

require 'minitest'

class Minitest::Runnable
  LOG = File.open('run_log.txt', 'w')

  Minitest.after_run { LOG.close }

  class << self
    alias :old_run_one_method :run_one_method

    def run_one_method klass, method_name, reporter
      before = Coverage.peek_result
      old_run_one_method klass, method_name, reporter
      after = Coverage.peek_result
      LOG.puts JSON.dump [ klass.name, method_name.to_s, before, after ]
    end
  end
end