How Can I Fake A MultiPolygon Field? - django

Question

I am creating a Django factory for a model that contains a MultiPolygonField. It is throwing an error when I run the test. Detail below.
I have created a special provider to fake this field. The code is taken from the Django docs:
from django.contrib.gis.geos import (
Polygon,
MultiPolygon,
)
import factory
from faker import Faker
from faker.providers import BaseProvider
fake = Faker()
class Provider(BaseProvider):
def mpoly(self):
p1 = Polygon( ((0, 0), (0, 1), (1, 1), (0, 0)) )
p2 = Polygon( ((1, 1), (1, 2), (2, 2), (1, 1)) )
mpoly = MultiPolygon(p1, p2)
return mpoly
fake.add_provider(Provider)
class GeographyFactory(factory.DjangoModelFactory):
"""
A Factory to generate mock GeographyFactory objects to be used
in tests.
"""
class Meta:
model = 'location.Geography'
name = factory.Faker('name')
mpoly = fake.mpoly
The error I get when I run the tests, however, has stumped me.
TypeError: Cannot set Geography SpatialProxy (MULTIPOLYGON) with value of type: <class 'method'>
It seems to suggest that I am not returning the right type, but I can't figure out what it wants instead of the MultiPolygon object I am returning.
Why does it think I am returning <class 'method'>?
Any suggestions would be most welcome!

Answer 1

I would suggest defining a custom fuzzy attribute, which would allow some randomness in your tests.
import factory
import factory.fuzzy
from factory import random
class FuzzyPolygon(factory.fuzzy.BaseFuzzyAttribute):
"""Yields random polygon"""
def __init__(self, length=None, **kwargs):
if length is None:
length = random.randgen.randrange(3, 20, 1)
if length < 3:
raise Exception("Polygon needs to be 3 or greater in length.")
self.length = length
super().__init__(**kwargs)
def get_random_coords(self):
return (
factory.Faker("latitude").generate({}),
factory.Faker("longitude").generate({}),
)
def fuzz(self):
prefix = suffix = self.get_random_coords()
coords = [self.get_random_coords() for __ in range(self.length - 1)]
return Polygon([prefix] + coords + [suffix])
class FuzzyMultiPolygon(factory.fuzzy.BaseFuzzyAttribute):
"""Yields random multipolygon"""
def __init__(self, length=None, **kwargs):
if length is None:
length = random.randgen.randrange(2, 20, 1)
if length < 2:
raise Exception("MultiPolygon needs to be 2 or greater in length.")
self.length = length
super().__init__(**kwargs)
def fuzz(self):
polygons = [FuzzyPolygon().fuzz() for __ in range(self.length)]
return MultiPolygon(*polygons)
Then you can use these in your DjangoModelfactory;
class GeographyFactory(factory.DjangoModelFactory):
"""
A Factory to generate mock GeographyFactory objects to be used
in tests.
"""
class Meta:
model = 'location.Geography'
name = factory.Faker('name')
mpoly = FuzzyMultiPolygon()