Question

say we have a ruby file.rb like:

if __FILE__ == $0 then
  if ARGV[0] == 'foo'
    puts "working"
    # Dir.chdir(../)
    v = Someclass.new
    v.do_something
  end
end

it suppose to print working only if the file was triggered like ruby file.rb foo.
My question: how can that kind of stuf be tested within rspec?

My try is below. The file ran but not in the scope of rspec test:
Dir expected :chdir with (any args) once, but received it 0 times

it 'should work' do
  FILE = File.expand_path('file.rb')
  RUBY = File.join(Config::CONFIG['bindir'], Config::CONFIG['ruby_install_name'])
  @v = Someclass.new
  Someclass.should_receive(:new).and_return @v
  @v.should_receive(:do_something)

  `#{RUBY} #{FILE} foo`
end

Answer 1

Backticks runs new shell, executes command, and returns result as a string. Thats why it runs outside your scope. Backticks does not care about contents of your script: ruby, bash, or something else.

chdir, of course, applied only to this new shell, so there seems no way to check you sample script for directory changing (except of tracing system calls). Maybe some ‘real’ script will do something, output more, thus providing more possibilities to check it.