old_contents: import os
  import tempfile
  
  from .io import invoke
  
  
  class Interpreter(object):
      # Assuming whatever is called "js" on the path is likely to work best
      known_engines = ['js', 'rhino']
  
      def __init__(self, exes=None):
          engines = exes if exes else self.known_engines
          self.exe = self.detect(engines)
  
          if not self.exe:
              raise RuntimeError("No js engine could be found, tried: %s"
                                 % ', '.join(engines))
  
      def detect(self, engines):
          found = None
  
          for engine in engines:
              # NOTE: Very platform specific
              success, stdout, stderr = invoke(['which', engine])
              exe = stdout
  
              # command exists, try executing a module on it
              if success:
                  if self.run_test_module(exe):
                      found = exe
                      break
  
          return found
  
      def run_test_module(self, exe):
          (fd, filepath) = tempfile.mkstemp()
          try:
              content = (
                  'try {'
                  '  console.log(1 + 3);'  # node.js
                  '} catch (e) {'
                  '  if (e.name !== "ReferenceError") {'
                  '    throw e;'
                  '  }'
                  '  print(1 + 3);'  # rhino/spidermonkey
                  '}')
              os.write(fd, content)
  
              success, stdout, stderr = invoke([exe, filepath])
              if success and '4' == stdout.strip():
                  return True
          finally:
              os.close(fd)
              os.unlink(filepath)
  
      def run_module(self, filepath):
          success, stdout, stderr = invoke([self.exe, filepath])
          return success, stderr
  
new_contents: import os
  import tempfile
  
  from .io import invoke
  
  
  class Interpreter(object):
      # Assuming whatever is called "js" on the path is likely to work best
      known_engines = ['js', 'rhino']
  
      def __init__(self, exes=None):
          engines = exes if exes else self.known_engines
          self.exe = self.detect(engines)
  
          if not self.exe:
              raise RuntimeError("No js engine could be found, tried: %s"
                                 % ', '.join(engines))
  
      def detect(self, engines):
          found = None
  
          for engine in engines:
              # NOTE: Very platform specific
              success, stdout, stderr = invoke(['which', engine])
              exe = stdout
  
              # command exists, try executing a module on it
              if success:
                  if self.run_test_module(exe):
                      found = exe
                      break
  
          return found
  
      def run_test_module(self, exe):
          (fd, filepath) = tempfile.mkstemp()
          try:
              content = (
                  'try {'
                  '  print;'
                  '} catch (e) {'
                  '  if (e.name !== "ReferenceError") {'
                  '    throw e;'
                  '  }'
                  '  print = console.log;'  # node.js
                  '}'
                  'print(1 + 3);')
              os.write(fd, content)
  
              success, stdout, stderr = invoke([exe, filepath])
              if success and '4' == stdout.strip():
                  return True
          finally:
              os.close(fd)
              os.unlink(filepath)
  
      def run_module(self, filepath):
          success, stdout, stderr = invoke([self.exe, filepath])
          return success, stderr
  
subject: rewrite js test