old_contents: import pandas_vectors as pv
  
  # TODO: write some tests!
  
new_contents: import pandas_vectors as pv
  import pandas as pd
  import numpy as np
  
  import unittest
  
  class PvTest(unittest.TestCase):
      def test_indexer(self):
          self.assertListEqual(pv.indexer('a'), ['a_x', 'a_y', 'a_z'])
          self.assertListEqual(pv.indexer(['a']), ['a_x', 'a_y', 'a_z'])
          self.assertListEqual(pv.indexer('abc'), ['abc_x', 'abc_y', 'abc_z'])
          self.assertListEqual(pv.indexer(['abc']), ['abc_x', 'abc_y', 'abc_z'])
          self.assertListEqual(pv.indexer(['abc','def']), ['abc_x', 'abc_y', 'abc_z', 'def_x', 'def_y', 'def_z'])
  
      def test_vectornames(self):
          pv.set_vectornames('pyr')
          self.assertListEqual(pv.indexer('a'), ['a_p', 'a_y', 'a_r'])
          pv.set_vectornames(['_l', '_m', '_n', '_o'])
          self.assertListEqual(pv.indexer('a'), ['a_l', 'a_m', 'a_n', 'a_o'])
          with pv.vectornames('xyz'):
              self.assertListEqual(pv.indexer('a'), ['a_x', 'a_y', 'a_z'])
          with pv.vectornames('xy'):
              self.assertListEqual(pv.indexer('a'), ['a_x', 'a_y'])
          self.assertListEqual(pv.indexer('a'), ['a_l', 'a_m', 'a_n', 'a_o'])
  
  
  if __name__ == '__main__':
      unittest.main()
  
subject: add basic tests