Adds test class for checking query durations

This is a first pass and I wrote it specifically so that it would fail
on the query in test_book.py

bookwyrm/tests/query_logger.py

@@ -0,0 +1,39 @@
+""" Log query runtimes for testing """
+import time
+
+
+class QueryLogger:
+    """Returns the sql and duration for any query run
+    Taken wholesale from:
+    https://docs.djangoproject.com/en/dev/topics/db/instrumentation/
+    """
+
+    def __init__(self):
+        self.queries = []
+
+    # pylint: disable=too-many-arguments
+    def __call__(self, execute, sql, params, many, context):
+        current_query = {"sql": sql, "params": params, "many": many}
+        start = time.monotonic()
+        try:
+            result = execute(sql, params, many, context)
+        except Exception as err: # pylint: disable=broad-except
+            current_query["status"] = "error"
+            current_query["exception"] = err
+            raise
+        else:
+            current_query["status"] = "ok"
+            return result
+        finally:
+            duration = time.monotonic() - start
+            current_query["duration"] = duration
+            self.queries.append(current_query)
+
+
+def raise_long_query_runtime(queries, threshold=0.0006):
+    """Raises an exception if any query took longer than the threshold"""
+    for query in queries:
+        if query["duration"] > threshold:
+            raise Exception( # pylint: disable=broad-exception-raised
+                "This looks like a slow query:", query["duration"], query["sql"]
+            )

bookwyrm/tests/views/books/test_book.py

@@ -7,6 +7,7 @@
 from django.contrib.auth.models import Group, Permission
 from django.contrib.contenttypes.models import ContentType
 from django.core.files.uploadedfile import SimpleUploadedFile
+from django.db import connection
 from django.http import Http404
 from django.template.response import TemplateResponse
 from django.test import TestCase
@@ -16,8 +17,9 @@
 from bookwyrm import forms, models, views
 from bookwyrm.activitypub import ActivitypubResponse
 from bookwyrm.tests.validate_html import validate_html
+from bookwyrm.tests.query_logger import QueryLogger, raise_long_query_runtime
 
-
+# pylint: disable=invalid-name
 class BookViews(TestCase):
     """books books books"""
 
@@ -68,9 +70,15 @@ def test_book_page(self):
         )
         request = self.factory.get("")
         request.user = self.local_user
-        with patch("bookwyrm.views.books.books.is_api_request") as is_api:
-            is_api.return_value = False
-            result = view(request, self.book.id)
+
+        query_logger = QueryLogger()
+        with connection.execute_wrapper(query_logger):
+            with patch("bookwyrm.views.books.books.is_api_request") as is_api:
+                is_api.return_value = False
+                result = view(request, self.book.id)
+
+            raise_long_query_runtime(query_logger.queries)
+
         self.assertIsInstance(result, TemplateResponse)
         validate_html(result.render())