django-override-storage 0.3.2
Django test helpers to manage file storage side effects.
License: MIT
Requires Python: >=2.7, !=3.0.*, !=3.1.*, !=3.2.*

Django Override Storage
=======================

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
------------

.. code-block:: bash

    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.

.. code-block:: python

    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.

.. code-block:: python

    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.

.. code-block:: python

    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
                storage_stats.save_cnt

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

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