Write tests confirming Binary Support response behavior

No functional change to the Zappa codebase is introduced by this commit.

This area of the application was untested. Tests introduced to ensure new
behavior discussed in zappa#908 does not cause
a regression.

tests/test_binary_support_settings.py

@@ -0,0 +1,12 @@
+API_STAGE = "dev"
+APP_FUNCTION = "app"
+APP_MODULE = "tests.test_wsgi_binary_support_app"
+BINARY_SUPPORT = True
+CONTEXT_HEADER_MAPPINGS = {}
+DEBUG = "True"
+DJANGO_SETTINGS = None
+DOMAIN = "api.example.com"
+ENVIRONMENT_VARIABLES = {}
+LOG_LEVEL = "DEBUG"
+PROJECT_NAME = "binary_support_settings"
+COGNITO_TRIGGER_MAPPING = {}

tests/test_handler.py

@@ -3,6 +3,7 @@
 
 from mock import Mock
 
+from tests.utils import is_base64
 from zappa.handler import LambdaHandler
 from zappa.utilities import merge_headers
 
@@ -225,6 +226,66 @@ def test_exception_handler_on_web_request(self):
         self.assertEqual(response["statusCode"], 500)
         mocked_exception_handler.assert_called()
 
+    def test_wsgi_script_binary_support_base64_behavior(self):
+        """
+        With Binary Support enabled, response mimetypes that are not text/* or application/json will be base64 encoded
+        """
+        lh = LambdaHandler("tests.test_binary_support_settings")
+
+        text_plain_event = {
+            "body": "",
+            "resource": "/{proxy+}",
+            "requestContext": {},
+            "queryStringParameters": {},
+            "headers": {
+                "Host": "1234567890.execute-api.us-east-1.amazonaws.com",
+            },
+            "pathParameters": {"proxy": "return/request/url"},
+            "httpMethod": "GET",
+            "stageVariables": {},
+            "path": "/textplain_mimetype_response1",
+        }
+
+        response = lh.handler(text_plain_event, None)
+
+        self.assertEqual(response["statusCode"], 200)
+        self.assertNotIn("isBase64Encoded", response)
+        self.assertFalse(is_base64(response["body"]))
+
+        text_arbitrary_event = {
+            **text_plain_event,
+            **{"path": "/textarbitrary_mimetype_response1"},
+        }
+
+        response = lh.handler(text_arbitrary_event, None)
+
+        self.assertEqual(response["statusCode"], 200)
+        self.assertNotIn("isBase64Encoded", response)
+        self.assertFalse(is_base64(response["body"]))
+
+        application_json_event = {
+            **text_plain_event,
+            **{"path": "/json_mimetype_response1"},
+        }
+
+        response = lh.handler(application_json_event, None)
+
+        self.assertEqual(response["statusCode"], 200)
+        self.assertNotIn("isBase64Encoded", response)
+        self.assertFalse(is_base64(response["body"]))
+
+        arbitrary_binary_event = {
+            **text_plain_event,
+            **{"path": "/arbitrarybinary_mimetype_response1"},
+        }
+
+        response = lh.handler(arbitrary_binary_event, None)
+
+        self.assertEqual(response["statusCode"], 200)
+        self.assertIn("isBase64Encoded", response)
+        self.assertTrue(response["isBase64Encoded"])
+        self.assertTrue(is_base64(response["body"]))
+
     def test_wsgi_script_on_cognito_event_request(self):
         """
         Ensure that requests sent by cognito behave sensibly

tests/test_wsgi_binary_support_app.py

@@ -0,0 +1,31 @@
+###
+# This test application exists to confirm how Zappa handles WSGI application
+# _responses_ when Binary Support is enabled.
+###
+
+import io
+import json
+
+from flask import Flask, Response, send_file
+
+app = Flask(__name__)
+
+
+@app.route("/textplain_mimetype_response1", methods=["GET"])
+def text_mimetype_response_1():
+    return Response(response="OK", mimetype="text/plain")
+
+
+@app.route("/textarbitrary_mimetype_response1", methods=["GET"])
+def text_mimetype_response_2():
+    return Response(response="OK", mimetype="text/arbitary")
+
+
+@app.route("/json_mimetype_response1", methods=["GET"])
+def json_mimetype_response_1():
+    return Response(response=json.dumps({"some": "data"}), mimetype="application/json")
+
+
+@app.route("/arbitrarybinary_mimetype_response1", methods=["GET"])
+def arbitrary_mimetype_response_1():
+    return Response(response=b"some binary data", mimetype="arbitrary/binary_mimetype")

tests/utils.py

@@ -1,3 +1,4 @@
+import base64
 import functools
 import os
 from contextlib import contextmanager
@@ -74,3 +75,11 @@ def stub_open(*args, **kwargs):
 
     with patch("__builtin__.open", stub_open):
         yield mock_open, mock_file
+
+
+def is_base64(test_string: str) -> bool:
+    # Taken from https://stackoverflow.com/a/45928164/3200002
+    try:
+        return base64.b64encode(base64.b64decode(test_string)).decode() == test_string
+    except Exception:
+        return False