text: from unittest import skipUnless
  
  from django.contrib.gis.db.models import fields
  from django.contrib.gis.geos import MultiPolygon, Polygon
  from django.core.exceptions import ImproperlyConfigured
  from django.db import connection, migrations, models
  from django.db.migrations.migration import Migration
  from django.db.migrations.state import ProjectState
  from django.test import TransactionTestCase, skipIfDBFeature, skipUnlessDBFeature
  
  try:
      GeometryColumns = connection.ops.geometry_columns()
      HAS_GEOMETRY_COLUMNS = True
  except NotImplementedError:
      HAS_GEOMETRY_COLUMNS = False
  
  
  class OperationTestCase(TransactionTestCase):
      available_apps = ["gis_tests.gis_migrations"]
      get_opclass_query = """
          SELECT opcname, c.relname FROM pg_opclass AS oc
          JOIN pg_index as i on oc.oid = ANY(i.indclass)
          JOIN pg_class as c on c.oid = i.indexrelid
          WHERE c.relname = %s
      """
  
      def tearDown(self):
          # Delete table after testing
          if hasattr(self, "current_state"):
              self.apply_operations(
                  "gis", self.current_state, [migrations.DeleteModel("Neighborhood")]
              )
          super().tearDown()
  
      @property
      def has_spatial_indexes(self):
          if connection.ops.mysql:
              with connection.cursor() as cursor:
                  return connection.introspection.supports_spatial_index(
                      cursor, "gis_neighborhood"
                  )
          return True
  
      def get_table_description(self, table):
          with connection.cursor() as cursor:
              return connection.introspection.get_table_description(cursor, table)
  
      def assertColumnExists(self, table, column):
          self.assertIn(column, [c.name for c in self.get_table_description(table)])
  
      def assertColumnNotExists(self, table, column):
          self.assertNotIn(column, [c.name for c in self.get_table_description(table)])
  
      def apply_operations(self, app_label, project_state, operations):
          migration = Migration("name", app_label)
          migration.operations = operations
          with connection.schema_editor() as editor:
              return migration.apply(project_state, editor)
  
      def set_up_test_model(self, force_raster_creation=False):
          test_fields = [
              ("id", models.AutoField(primary_key=True)),
              ("name", models.CharField(max_length=100, unique=True)),
              ("geom", fields.MultiPolygonField(srid=4326)),
          ]
          if connection.features.supports_raster or force_raster_creation:
              test_fields += [("rast", fields.RasterField(srid=4326, null=True))]
          operations = [migrations.CreateModel("Neighborhood", test_fields)]
          self.current_state = self.apply_operations("gis", ProjectState(), operations)
  
      def assertGeometryColumnsCount(self, expected_count):
          self.assertEqual(
              GeometryColumns.objects.filter(
                  **{
                      "%s__iexact" % GeometryColumns.table_name_col(): "gis_neighborhood",
                  }
              ).count(),
              expected_count,
          )
  
      def assertSpatialIndexExists(self, table, column, raster=False):
          with connection.cursor() as cursor:
              constraints = connection.introspection.get_constraints(cursor, table)
          if raster:
              self.assertTrue(
                  any(
                      "st_convexhull(%s)" % column in c["definition"]
                      for c in constraints.values()
                      if c["definition"] is not None
                  )
              )
          else:
              self.assertIn([column], [c["columns"] for c in constraints.values()])
  
      def alter_gis_model(
          self,
          migration_class,
          model_name,
          field_name,
          blank=False,
          field_class=None,
          field_class_kwargs=None,
      ):
          args = [model_name, field_name]
          if field_class:
              field_class_kwargs = field_class_kwargs or {"srid": 4326, "blank": blank}
              args.append(field_class(**field_class_kwargs))
          operation = migration_class(*args)
          old_state = self.current_state.clone()
          operation.state_forwards("gis", self.current_state)
          with connection.schema_editor() as editor:
              operation.database_forwards("gis", editor, old_state, self.current_state)
  
  
  class OperationTests(OperationTestCase):
      def setUp(self):
          super().setUp()
          self.set_up_test_model()
  
      def test_add_geom_field(self):
          """
          Test the AddField operation with a geometry-enabled column.
          """
          self.alter_gis_model(
              migrations.AddField, "Neighborhood", "path", False, fields.LineStringField
          )
          self.assertColumnExists("gis_neighborhood", "path")
  
          # Test GeometryColumns when available
          if HAS_GEOMETRY_COLUMNS:
              self.assertGeometryColumnsCount(2)
  
          # Test spatial indices when available
          if self.has_spatial_indexes:
              self.assertSpatialIndexExists("gis_neighborhood", "path")
  
      @skipUnless(HAS_GEOMETRY_COLUMNS, "Backend doesn't support GeometryColumns.")
      def test_geom_col_name(self):
          self.assertEqual(
              GeometryColumns.geom_col_name(),
              "column_name" if connection.ops.oracle else "f_geometry_column",
          )
  
      @skipUnlessDBFeature("supports_raster")
      def test_add_raster_field(self):
          """
          Test the AddField operation with a raster-enabled column.
          """
          self.alter_gis_model(
              migrations.AddField, "Neighborhood", "heatmap", False, fields.RasterField
          )
          self.assertColumnExists("gis_neighborhood", "heatmap")
  
          # Test spatial indices when available
          if self.has_spatial_indexes:
              self.assertSpatialIndexExists("gis_neighborhood", "heatmap", raster=True)
  
      def test_add_blank_geom_field(self):
          """
          Should be able to add a GeometryField with blank=True.
          """
          self.alter_gis_model(
              migrations.AddField, "Neighborhood", "path", True, fields.LineStringField
          )
          self.assertColumnExists("gis_neighborhood", "path")
  
          # Test GeometryColumns when available
          if HAS_GEOMETRY_COLUMNS:
              self.assertGeometryColumnsCount(2)
  
          # Test spatial indices when available
          if self.has_spatial_indexes:
              self.assertSpatialIndexExists("gis_neighborhood", "path")
  
      @skipUnlessDBFeature("supports_raster")
      def test_add_blank_raster_field(self):
          """
          Should be able to add a RasterField with blank=True.
          """
          self.alter_gis_model(
              migrations.AddField, "Neighborhood", "heatmap", True, fields.RasterField
          )
          self.assertColumnExists("gis_neighborhood", "heatmap")
  
          # Test spatial indices when available
          if self.has_spatial_indexes:
              self.assertSpatialIndexExists("gis_neighborhood", "heatmap", raster=True)
  
      def test_remove_geom_field(self):
          """
          Test the RemoveField operation with a geometry-enabled column.
          """
          self.alter_gis_model(migrations.RemoveField, "Neighborhood", "geom")
          self.assertColumnNotExists("gis_neighborhood", "geom")
  
          # Test GeometryColumns when available
          if HAS_GEOMETRY_COLUMNS:
              self.assertGeometryColumnsCount(0)
  
      @skipUnlessDBFeature("supports_raster")
      def test_remove_raster_field(self):
          """
          Test the RemoveField operation with a raster-enabled column.
          """
          self.alter_gis_model(migrations.RemoveField, "Neighborhood", "rast")
          self.assertColumnNotExists("gis_neighborhood", "rast")
  
      def test_create_model_spatial_index(self):
          if not self.has_spatial_indexes:
              self.skipTest("No support for Spatial indexes")
  
          self.assertSpatialIndexExists("gis_neighborhood", "geom")
  
          if connection.features.supports_raster:
              self.assertSpatialIndexExists("gis_neighborhood", "rast", raster=True)
  
      @skipUnlessDBFeature("supports_3d_storage")
      def test_add_3d_field_opclass(self):
          if not connection.ops.postgis:
              self.skipTest("PostGIS-specific test.")
  
          self.alter_gis_model(
              migrations.AddField,
              "Neighborhood",
              "point3d",
              field_class=fields.PointField,
              field_class_kwargs={"dim": 3},
          )
          self.assertColumnExists("gis_neighborhood", "point3d")
          self.assertSpatialIndexExists("gis_neighborhood", "point3d")
  
          with connection.cursor() as cursor:
              index_name = "gis_neighborhood_point3d_113bc868_id"
              cursor.execute(self.get_opclass_query, [index_name])
              self.assertEqual(
                  cursor.fetchall(),
                  [("gist_geometry_ops_nd", index_name)],
              )
  
      @skipUnlessDBFeature("can_alter_geometry_field", "supports_3d_storage")
      def test_alter_geom_field_dim(self):
          Neighborhood = self.current_state.apps.get_model("gis", "Neighborhood")
          p1 = Polygon(((0, 0), (0, 1), (1, 1), (1, 0), (0, 0)))
          Neighborhood.objects.create(name="TestDim", geom=MultiPolygon(p1, p1))
          # Add 3rd dimension.
          self.alter_gis_model(
              migrations.AlterField,
              "Neighborhood",
              "geom",
              False,
              fields.MultiPolygonField,
              field_class_kwargs={"srid": 4326, "dim": 3},
          )
          self.assertTrue(Neighborhood.objects.first().geom.hasz)
          # Rewind to 2 dimensions.
          self.alter_gis_model(
              migrations.AlterField,
              "Neighborhood",
              "geom",
              False,
              fields.MultiPolygonField,
              field_class_kwargs={"srid": 4326, "dim": 2},
          )
          self.assertFalse(Neighborhood.objects.first().geom.hasz)
  
      @skipUnlessDBFeature(
          "supports_column_check_constraints", "can_introspect_check_constraints"
      )
      def test_add_check_constraint(self):
          Neighborhood = self.current_state.apps.get_model("gis", "Neighborhood")
          poly = Polygon(((0, 0), (0, 1), (1, 1), (1, 0), (0, 0)))
          constraint = models.CheckConstraint(
              check=models.Q(geom=poly),
              name="geom_within_constraint",
          )
          Neighborhood._meta.constraints = [constraint]
          with connection.schema_editor() as editor:
              editor.add_constraint(Neighborhood, constraint)
          with connection.cursor() as cursor:
              constraints = connection.introspection.get_constraints(
                  cursor,
                  Neighborhood._meta.db_table,
              )
              self.assertIn("geom_within_constraint", constraints)
  
  
  @skipIfDBFeature("supports_raster")
  class NoRasterSupportTests(OperationTestCase):
      def test_create_raster_model_on_db_without_raster_support(self):
          msg = "Raster fields require backends with raster support."
          with self.assertRaisesMessage(ImproperlyConfigured, msg):
              self.set_up_test_model(force_raster_creation=True)
  
      def test_add_raster_field_on_db_without_raster_support(self):
          msg = "Raster fields require backends with raster support."
          with self.assertRaisesMessage(ImproperlyConfigured, msg):
              self.set_up_test_model()
              self.alter_gis_model(
                  migrations.AddField,
                  "Neighborhood",
                  "heatmap",
                  False,
                  fields.RasterField,
              )
  