old_contents: import os
  import sys
  import unittest
  
  
  def suite():
      MODULE_DIR = os.path.join(os.path.dirname(__file__), '..')
      MODULE_DIR = os.path.abspath(MODULE_DIR)
      sys.path.insert(0, MODULE_DIR)
      sys.path.insert(0, os.path.dirname(__file__))
  
      SUB_UNITS = os.path.dirname(__file__)
      SUB_UNITS = os.listdir(SUB_UNITS)
      SUB_UNITS = [
          filename[:-3]
          for filename in SUB_UNITS
          if filename.startswith('test_')
      ]
  
      os.chdir(os.path.dirname(__file__))
      loader = unittest.TestLoader()
      return loader.loadTestsFromNames(SUB_UNITS)
  
new_contents: from os import walk, chdir
  from os.path import join, dirname, splitext, abspath, relpath
  import sys
  import unittest
  
  MODULE_DIR = join(dirname(__file__), '..')
  MODULE_DIR = abspath(MODULE_DIR)
  
  
  def walker(opath='.'):
      for path, folders, files in walk(opath):
          for filename in files:
              if filename.startswith('test_') and filename.endswith('.py'):
                  rpath = relpath(path, opath)
  
                  yield (rpath + '.' + splitext(filename)[0]).strip('.')
  
  
  def suite():
      sys.path.insert(0, MODULE_DIR)
      sys.path.insert(0, dirname(__file__))
  
      SUB_UNITS = dirname(__file__)
      SUB_UNITS = walker(SUB_UNITS)
  
      chdir(dirname(__file__))
  
      return unittest.TestLoader().loadTestsFromNames(SUB_UNITS)
  
subject: Rework for tests in subdirectories