new_contents: import unittest
  
  
  class RoadSortKeyTest(unittest.TestCase):
  
      def _call_fut(self, props, zoom=15, shape=None, fid=None):
          from TileStache.Goodies.VecTiles.transform import road_sort_key
          _, newprops, fid = road_sort_key(shape, props, fid, zoom)
          sort_key = newprops['sort_key']
          return sort_key
  
      def _call_fut_with_prop(self, keyval, zoom=15, shape=None,
                              fid=None):
          key, val = keyval.split('=')
          return self._call_fut({key: val}, zoom, shape, fid)
  
      def _call_fut_with_float_prop(self, keyval, zoom=15, shape=None,
                                    fid=None):
          key, val = keyval.split('=')
          val = float(val)
          return self._call_fut({key: val}, zoom, shape, fid)
  
      def test_layer_low(self):
          sort_key = self._call_fut_with_float_prop('layer=-5')
          self.assertEqual(300, sort_key)
  
      def test_tunnel(self):
          sort_key = self._call_fut_with_prop('tunnel=yes')
          self.assertEqual(315, sort_key)
  
      def test_empty(self):
          sort_key = self._call_fut({})
          self.assertEqual(325, sort_key)
  
      def test_railway_service_highway(self):
          props = dict(
              railway='rail',
              service='unknown',
              highway='service'
          )
          sort_key = self._call_fut(props)
          self.assertEqual(334, sort_key)
  
      def test_link(self):
          sort_key = self._call_fut_with_prop('highway=primary_link')
          self.assertEqual(338, sort_key)
  
      def test_railway(self):
          sort_key = self._call_fut_with_prop('railway=rail')
          self.assertEqual(343, sort_key)
  
      def test_motorway(self):
          sort_key = self._call_fut_with_prop('highway=motorway')
          self.assertEqual(344, sort_key)
  
      def test_bridge(self):
          sort_key = self._call_fut_with_prop('bridge=yes')
          self.assertEqual(365, sort_key)
  
      def test_aerialway(self):
          sort_key = self._call_fut_with_prop('aerialway=gondola')
          self.assertEqual(377, sort_key)
  
      def test_layer_high(self):
          sort_key = self._call_fut_with_float_prop('layer=5')
          self.assertEqual(385, sort_key)
  
subject: Add road sort key tests