old_contents: """Tests for coverage.data"""
  
  import unittest
  from coverage.data import CoverageData
  
  class DataTest(unittest.TestCase):
      def test_reading(self):
          covdata = CoverageData()
          covdata.read()
          self.assertEqual(covdata.summary(), {})
  
new_contents: """Tests for coverage.data"""
  
  from coverage.data import CoverageData
  from coveragetest import CoverageTest
  
  class DataTest(CoverageTest):
      def test_reading(self):
          covdata = CoverageData()
          covdata.read()
          self.assertEqual(covdata.summary(), {})
  
subject: Use our CoverageTest base class to get isolation (in a new directory) for the data tests.