old_contents: import unittest
  from ooni.utils import pushFilenameStack
  
  class TestUtils(unittest.TestCase):
      def test_pushFilenameStack(self):
          f = open("dummyfile", "w+")
          f.write("0\n")
          f.close()
          for i in xrange(1, 5):
              f = open("dummyfile.%s" % i, "w+")
              f.write("%s\n" % i)
              f.close()
  
          pushFilenameStack("dummyfile")
          for i in xrange(1, 5):
              f = open("dummyfile.%s" % i)
              c = f.readlines()[0].strip()
              self.assertEqual(str(i-1), str(c))
              f.close()
  
  
new_contents: import os
  import unittest
  from ooni.utils import pushFilenameStack
  basefilename = os.path.abspath('dummyfile')
  class TestUtils(unittest.TestCase):
      def test_pushFilenameStack(self):
          f = open(basefilename, "w+")
          f.write("0\n")
          f.close()
          for i in xrange(1, 5):
              f = open(basefilename+".%s" % i, "w+")
              f.write("%s\n" % i)
              f.close()
  
          pushFilenameStack(basefilename)
          for i in xrange(1, 5):
              f = open(basefilename+".%s" % i)
              c = f.readlines()[0].strip()
              self.assertEqual(str(i-1), str(c))
              f.close()
  
  
subject: Use absolute filepath instead of relative