[Django]-What is the clean way to unittest FileField in django?

Django provides a great way to do this – use a SimpleUploadedFile or a TemporaryUploadedFile. SimpleUploadedFile is generally the simpler option if all you need to store is some sentinel data:

from django.core.files.uploadedfile import SimpleUploadedFile

my_model.file_field = SimpleUploadedFile(
    "best_file_eva.txt",
    b"these are the file contents!"   # note the b in front of the string [bytes]
)

It’s one of django’s magical features-that-don’t-show-up-in-the-docs :). However it is referred to here and implemented here.

Limitations

Note that you can only put bytes in a SimpleUploadedFile since it’s implemented using BytesIO behind the scenes. If you need more realistic, file-like behavior you can use TemporaryUploadedFile.

For Python 2

If you’re stuck on python 2, skip the b prefix in the content:

my_model.file_field = SimpleUploadedFile(
    "best_file_eva.txt",
    "these are the file contents!" # no b
)

I normally test filefields in models using doctest

>>> from django.core.files import File
>>> s = SimpleModel()
>>> s.audio_file = File(open("media/testfiles/testaudio.wav"))
>>> s.save()
>>> ...
>>> s.delete()

If I need to I also test file uploads with test clients.

As for fixtures, I simply copy the files i need in a test folder, after modifying the paths in the fixture.

e.g.

In a fixture containing models with filefiels pointing to a directory named “audio”, you replace “audio”: “audio/audio.wav” with “audio”: “audio/test/audio.wav” .
Now all you have to do is copy the test folder, with the necessary files, in “audio” in the test setUp and then delete it in tearDown.

Not the cleanest way ever i think, but that’s what i do.

If you just want to create an object that requires FileField and don’t want to use this field then you can just pass any (existing or not) relative path like this:

example_object = models.ExampleModel({'file': "foo.bar"})
example_object.save()

Then it’s ready for use.

I guess that easiest way is to use ContentFile class:

file = ContentFile('text', 'name')
my_model = MyModel()
my_model.file = file
my_model.save()

There is some way to mock storage.

After reading django source code, the below is my implementation to avoid uploading file to s3 regardless of using default storage or assigning the storage in filefield or imagefield.

from unittest.mock import patch
from django.db.models.fields.files import FileField, FieldFile, ImageField, ImageFieldFile
from django.core.files.storage import FileSystemStorage
from rest_framework.test import APITestCase


class CustomFileSystemStorage(FileSystemStorage):
    def url(self, *args, **kwargs):
        return self.path(*args, **kwargs)


class CustomFieldFile(FieldFile):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.storage = CustomFileSystemStorage()
        
        
class CustomImageFieldFile(ImageFieldFile):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.storage = CustomFileSystemStorage()


class PatchMeta(type):
    """A metaclass to patch all inherited classes."""

    def __new__(meta, name, bases, attrs):
        cls = type.__new__(meta, name, bases, attrs)
        cls = patch.object(ImageField, 'attr_class', CustomImageFieldFile)(cls)
        cls = patch.object(FileField, 'attr_class', CustomFieldFile)(cls)
        return cls


class CustomBaseTestCase(APITestCase, metaclass=PatchMeta):
    """You can inherit this class to do any testcase for mocking storage"""
    pass

With inheriting CustomBaseTestCase class, you can change your storage to avoid uploading files to any server