Monkeypatch builtins for use in py.tests

test.py

import __builtin__

def test_raw_input(monkeypatch):
  """ Get user input without actually having a user type letters using monkeypatch """
  def mock_raw_input(*args, **kwargs):
    """ Act like someone just typed 'yolo'. """
    return 'yolo';
    
  monkeypatch.setattr(__builtin__, 'raw_input', mock_raw_input)
  
  # retval should now contain 'yolo'
  retval = raw_input()
  
  assert retval == 'yolo'