Add test for saving files using bytes/strings and File/ContentFile.

2 of these tests currently fail due to issue jschneier#708.
They use moto to mock s3 at a lower level and actually get the right error to surface.

tests/settings.py

@@ -10,3 +10,8 @@
 SECRET_KEY = 'hailthesunshine'
 
 USE_TZ = True
+
+
+AWS_STORAGE_BUCKET_NAME = "test_bucket"
+AWS_ACCESS_KEY_ID = "testing_key_id"
+AWS_SECRET_ACCESS_KEY = "testing_access_key"

tests/test_s3boto3.py

@@ -2,16 +2,19 @@
 import pickle
 import threading
 from datetime import datetime
+from io import BytesIO, StringIO
 from textwrap import dedent
 from unittest import mock, skipIf
 from urllib.parse import urlparse
 
+from boto3 import resource
 from botocore.exceptions import ClientError
 from django.conf import settings
 from django.core.exceptions import ImproperlyConfigured
-from django.core.files.base import ContentFile
+from django.core.files.base import ContentFile, File
 from django.test import TestCase, override_settings
 from django.utils.timezone import is_aware, utc
+from moto import mock_s3
 
 from storages.backends import s3boto3
 
@@ -642,3 +645,59 @@ def test_override_init_argument(self):
         self.assertEqual(storage.location, 'foo1')
         storage = s3boto3.S3Boto3Storage(location='foo2')
         self.assertEqual(storage.location, 'foo2')
+
+
+@mock_s3
+class S3Boto3StorageTestsWithMoto(TestCase):
+    """
+    These tests use the moto library to mock S3, rather than unittest.mock.
+    This is better because more of boto3's internal code will be run in tests.
+
+    For example this issue
+    https://github.com/jschneier/django-storages/issues/708
+    wouldn't be caught using unittest.mock, since the error occurs in boto3's internals.
+
+    Using mock_s3 as a class decorator automatically decorates methods,
+    but NOT classmethods or staticmethods.
+    """
+    @classmethod
+    @mock_s3
+    def setUpClass(cls):
+        super().setUpClass()
+        # create a bucket specified in settings.
+        cls.bucket = resource("s3").Bucket(settings.AWS_STORAGE_BUCKET_NAME)
+        cls.bucket.create()
+        # create a S3Boto3Storage backend instance.
+        cls.s3boto3_storage = s3boto3.S3Boto3Storage()
+
+    def test_save_bytes_file(self):
+        self.s3boto3_storage.save("bytes_file.txt", File(BytesIO(b"foo1")))
+
+        self.assertEqual(
+            b"foo1",
+            self.bucket.Object("bytes_file.txt").get()['Body'].read(),
+        )
+
+    def test_save_string_file(self):
+        self.s3boto3_storage.save("string_file.txt", File(StringIO("foo2")))
+
+        self.assertEqual(
+            b"foo2",
+            self.bucket.Object("string_file.txt").get()['Body'].read(),
+        )
+
+    def test_save_bytes_content(self):
+        self.s3boto3_storage.save("bytes_content.txt", ContentFile(b"foo3"))
+
+        self.assertEqual(
+            b"foo3",
+            self.bucket.Object("bytes_content.txt").get()['Body'].read(),
+        )
+
+    def test_save_string_content(self):
+        self.s3boto3_storage.save("string_content.txt", ContentFile("foo4"))
+
+        self.assertEqual(
+            b"foo4",
+            self.bucket.Object("string_content.txt").get()['Body'].read(),
+        )