A spec_helper to assist in testing executable file behaviour, assumes your Gemfile includes the Open4 gem.

spec_helper.rb

require 'bundler'
Bundler.require(:test)

def run(*args)
  output = Struct.new(:pid, :stdout, :stderr)

  status = Open4.popen4(*args) do |pid, stdin, stdout, stderr|
    output = output.new pid, stdout.read, stderr.read
  end

  [status, output]
end