django-override-storage 0.3.0

Django test helpers to manage file storage side effects.

Stop filling up your disk with test files or your code with file system mocks!

This project provides tools to help you reduce the side effects of using FileFields during tests.

Installation

pip install django-override-storage

Simple Usage

Calling override_storage() without any arguments will patch all FileField fields to store the contents of the file in an in-memory cache and returns the fields to their previous storages when leaving its context. The storage cache is deleted at the end of each test or when exiting the context manager depending on how it is called.

It can be used similarly to django.test.utils.override_settings: as a class decorator, a method decorator or a context manager.

from django.core.files.base import ContentFile
from django.test import TestCase

from override_storage import override_storage
from override_storage.storage import LocMemStorage

from .models import SimpleModel

class OverrideStorageTestCase(TestCase):

    def test_context_manager(self):
        with override_storage():
            # By default, all files saved to in memory cache.
            obj = SimpleModel()
            obj.upload_file.save('test.txt', ContentFile('content'))

            # Get your file back!
            content = obj.upload_file.read()

    @override_storage(storage=LocMemStorage())
    def test_method_decorator(self):
        # You can also specify to replace all storage backends with a
        # storage instance of your choosing. Depending on the storage type,
        # this could mean all writes will persist for the life of the
        # instance. This does not really matter if you wanted to pass in a
        # FileSystemStorage instance as those writes will be persisted
        # regardless.
        ...

    @override_storage(storage=LocMemStorage)
    def test_method_decorator(self):
        # Passing in a class will create a new instance for every test.

    @override_storage()
    def test_method_decorator(self):
        # Used as a method decorator.
        ...


@override_storage()
class OverrideStorageClassTestCase(TestCase):
    # You can also wrap classes.
    ...

It can also be used globally through a custom test runner. This can be achieved by setting the TEST_RUNNER setting in your settings file or however else you may choose to define the Django test runner.

Warning

TEST_RUNNER only sets up the replacement storage once at the start of the tests as there are no hooks into the setUp / tearDown methods of the test class. Using override_storage.LocMemStorageDiscoverRunner will share a single in memory cache across all tests. While this shouldn’t affect your tests, if you write a lot of big files, you may run out of memory.

TEST_RUNNER = 'override_storage.LocMemStorageDiscoverRunner'

Storage information

Like override_storage, locmem_stats_override_storage patches all FileField fields to store the contents of the file in an in-memory cache and returns the fields to their previous storages when leaving its context.

In addition to the normal functionality, it returns an object with information about the calls to the _open and _save methods of the test storage. In general it records which fields have had files read from or written to them and the names of the files are recorded.

from django.core.files.base import ContentFile
from django.test import TestCase

from override_storage import locmem_stats_override_storage

from .models import SimpleModel

class OverrideStorageTestCase(TestCase):

    def test_context_manager(self):
        with locmem_stats_override_storage() as storage_stats:
            # All files saved to in memory cache.
            obj = SimpleModel()
            obj.upload_file.save('test.txt', ContentFile('content'))

            # Check how many files have been saved
            self.storage_stats.save_cnt

            # Check which fields were read or saved
            self.storage_stats.fields_saved
            self.storage_stats.fields_read

            # Get a list of names, by field, which have been saved or read.
            self.storage_stats.reads_by_field
            self.storage_stats.saves_by_field

            # Get your file back!
            content = obj.upload_file.read()

    @locmem_stats_override_storage(name='storage_stats')
    def test_method_decorator(self, storage_stats):
        # access to storage stats by specifying `name` which is the name of
        # the kwarg to be used in the function signature.
        ...


@locmem_stats_override_storage(name='storage_stats')
class OverrideStorageClassTestCase(TestCase):
    storage_stats = None

    # access to storage stats by specifying attr_name
    ...