Django Image field

For the ImageField to work it's necessary to have the Pillow library installed.

Django Models

The setup of the model containing the image field can be done in the following way.

class BookInformation(models.Model):
    #...
    cover_image = models.ImageField(upload_to="covers/", null=True)
    #...

Note that the upload_to option corresponds to the path in which the images are stored/saved in the media folder. In this case the path will be .../library_project/media/covers/.

Factory Boy mock data

The easiest way to generate mock images data with factory boy is with the factory.django.ImageField() method just like the example below.

class BookInformationFactory(factory.django.DjangoModelFactory):
    #...
    cover_image = factory.django.ImageField(color=factory.Faker("color"))
    #...

Note that the color option can be Hardcoded with something like color="blue" and that will result in the generation of images with the color blue. In this case, factory.Faker("color") will generate random color names which will result in the generation of images with diferent colors for each cover_image.

Django Model Serializer

Considering the previous factory, here is the correspondent serializer for POST and PUT requests.

class BookInformationCreateUpdateSerializer(serializers.ModelSerializer):
    cover_image = serializers.ImageField(required=False, allow_empty_file=True)

    class Meta:
        model = BookInformation
        fields = [     
        #... , 
        "cover_image", 
        #... ,
        ]

API View

class BookInformationViewset(viewsets.ModelViewSet):
    queryset = BookInformation.objects.all()
    serializer_class = BookInformationCreateUpdateSerializer

ImageField Views Tests

To test the views that involve the cover_image attribute you can simply generate an image based on the implemented factory for the cover image just like the example below.

from PIL import Image
import shutil
from ..fixtures import REMOVE_MEDIA_FILES_PATH

class BookCreateViewTestCase(APITestCase):
    def setUp(self):
        #...
        self.data = {
            "cover_image": #...
            #...
        }

    def tearDown(self):
        shutil.rmtree(REMOVE_MEDIA_FILES_PATH)

    def test_create_with_image(self):
        cover = BookInformationFactory.create().cover_image

        self.data["cover_image"] = cover
        res = self.client.post(self.url, self.data, format="multipart")

        self.assertEqual(res.status_code, status.HTTP_201_CREATED)
        self.assertEqual(
            BookInformation.objects.first().cover_image.read(), BookInformation.objects.last().cover_image.read()
        )

    def test_create_with_image_failure(self):
        self.data["cover_image"] = Image.new(mode="RGB", size=(20, 20))

        res = self.client.post(self.url, self.data, format="multipart")

        self.assertEqual(res.status_code, status.HTTP_400_BAD_REQUEST)

It is crucial that the format option in set to "multipart" for the test to work. It is also important to have the tearDown method implemented in order to delete the images saved on the folder refered previously (.../library_project/media/covers/).

ImageField Views Tests using temp files

Other way of implementing a view test that includes an ImageField is with the SimpleUploadedFile() method.

The code below will generate an Image with the PIL Library, save it in a temporary file, process it with SimpleUploadedFile() method and then make the POST request.

In this case the tearDown method still needs to be implemented, since the POST request will save the image in the media folder.

from django.core.files.uploadedfile import SimpleUploadedFile
from io import BytesIO
from PIL import Image
import shutil

class BookCreateViewTestCase(APITestCase):
    def setUp(self):
        self.data = {
            "cover_image": #...
            #...
        }

    def tearDown(self):
        shutil.rmtree(REMOVE_MEDIA_FILES_PATH)

    def test_create_with_image(self):
        base_image = Image.new(mode="RGB", size=(20, 20))

        tempFile = BytesIO()
        base_image.save(tempFile, format="JPEG")
        tempFile.seek(0)

        with tempFile as temp:
            read_image = SimpleUploadedFile("sample.jpg", temp.read(), content_type="image/jpeg")
            self.data["cover_image"] = read_image

            res = self.client.post(self.url, self.data, format="multipart")
            read_image.seek(0)

        self.assertEqual(res.status_code, status.HTTP_201_CREATED)
        self.assertEqual(BookInformation.objects.first().cover_image.read(), read_image.read())