text: from __future__ import unicode_literals
  
  import json
  
  from django.contrib.gis.geos import LinearRing, Point, Polygon
  from django.core import serializers
  from django.test import TestCase, mock, skipUnlessDBFeature
  from django.utils import six
  
  from .models import City, MultiFields, PennsylvaniaCity
  
  
  @skipUnlessDBFeature("gis_enabled")
  class GeoJSONSerializerTests(TestCase):
      fixtures = ['initial']
  
      def test_builtin_serializers(self):
          """
          'geojson' should be listed in available serializers.
          """
          all_formats = set(serializers.get_serializer_formats())
          public_formats = set(serializers.get_public_serializer_formats())
  
          self.assertIn('geojson', all_formats),
          self.assertIn('geojson', public_formats)
  
      def test_serialization_base(self):
          geojson = serializers.serialize('geojson', City.objects.all().order_by('name'))
          try:
              geodata = json.loads(geojson)
          except Exception:
              self.fail("Serialized output is not valid JSON")
          self.assertEqual(len(geodata['features']), len(City.objects.all()))
          self.assertEqual(geodata['features'][0]['geometry']['type'], 'Point')
          self.assertEqual(geodata['features'][0]['properties']['name'], 'Chicago')
  
      def test_geometry_field_option(self):
          """
          When a model has several geometry fields, the 'geometry_field' option
          can be used to specify the field to use as the 'geometry' key.
          """
          MultiFields.objects.create(
              city=City.objects.first(), name='Name', point=Point(5, 23),
              poly=Polygon(LinearRing((0, 0), (0, 5), (5, 5), (5, 0), (0, 0))))
  
          geojson = serializers.serialize('geojson', MultiFields.objects.all())
          geodata = json.loads(geojson)
          self.assertEqual(geodata['features'][0]['geometry']['type'], 'Point')
  
          geojson = serializers.serialize('geojson', MultiFields.objects.all(),
              geometry_field='poly')
          geodata = json.loads(geojson)
          self.assertEqual(geodata['features'][0]['geometry']['type'], 'Polygon')
  
      def test_fields_option(self):
          """
          The fields option allows to define a subset of fields to be present in
          the 'properties' of the generated output.
          """
          PennsylvaniaCity.objects.create(name='Mansfield', county='Tioga', point='POINT(-77.071445 41.823881)')
          geojson = serializers.serialize('geojson', PennsylvaniaCity.objects.all(),
              fields=('county', 'point'))
          geodata = json.loads(geojson)
          self.assertIn('county', geodata['features'][0]['properties'])
          self.assertNotIn('founded', geodata['features'][0]['properties'])
  
      def test_srid_option(self):
          geojson = serializers.serialize('geojson', City.objects.all().order_by('name'), srid=2847)
          geodata = json.loads(geojson)
          self.assertEqual(
              [int(c) for c in geodata['features'][0]['geometry']['coordinates']],
              [1564802, 5613214])
  
      @mock.patch('django.contrib.gis.serializers.geojson.HAS_GDAL', False)
      def test_without_gdal(self):
          # Without coordinate transformation, the serialization should succeed:
          serializers.serialize('geojson', City.objects.all())
          with six.assertRaisesRegex(self, serializers.base.SerializationError, '.*GDAL is not installed'):
              # Coordinate transformations need GDAL
              serializers.serialize('geojson', City.objects.all(), srid=2847)
  
      def test_deserialization_exception(self):
          """
          GeoJSON cannot be deserialized.
          """
          with self.assertRaises(serializers.base.SerializerDoesNotExist):
              serializers.deserialize('geojson', '{}')
  