Add `Rendition.cache_backend` tests

- to ensure correct backend is selected
- for purging image renditions with cache

wagtail/images/tests/test_management_commands.py

@@ -3,7 +3,7 @@ import warnings
 from io import StringIO
 
 from django.core import management
-from django.test import TestCase
+from django.test import TestCase, override_settings
 
 from .utils import Image, get_test_image_file
 
@@ -12,6 +12,8 @@ Rendition = Image.get_rendition_model()
 
 
 class TestUpdateImageRenditions(TestCase):
+    REAESC = re.compile(r"\x1b[^m]*m")
+
     @classmethod
     def setUpTestData(cls):
         cls.image = Image.objects.create(
@@ -65,7 +67,7 @@ class TestUpdateImageRenditions(TestCase):
         renditions = Rendition.objects.all()
         total_renditions = len(renditions)
         output = self.run_command()
-        output_string = self.reaesc.sub("", output.read())
+        output_string = self.REAESC.sub("", output.read())
         # checking if the number of renditions regenerated equal total_renditions
         self.assertEqual(
             output_string,
@@ -82,7 +84,7 @@ class TestUpdateImageRenditions(TestCase):
         renditions = Rendition.objects.all()
         total_renditions = len(renditions)
         output = self.run_command(purge_only=True)
-        output_string = self.reaesc.sub("", output.read())
+        output_string = self.REAESC.sub("", output.read())
         # checking if the number of renditions purged equal total_renditions
         self.assertEqual(
             output_string,
@@ -94,3 +96,23 @@ class TestUpdateImageRenditions(TestCase):
         renditions_now = Rendition.objects.all()
         total_renditions_now = len(renditions_now)
         self.assertEqual(total_renditions_now, 0)
+
+    @override_settings(
+        CACHES={"default": {"BACKEND": "django.core.cache.backends.locmem.LocMemCache"}}
+    )
+    def test_image_renditions_with_cache(self):
+        total_renditions = get_image_model().get_rendition_model().objects.count()
+        output = self.run_command()
+        output_string = self.REAESC.sub("", output.read())
+        self.assertEqual(
+            output_string,
+            f"Successfully regenerated {total_renditions} image rendition(s)\n",
+        )
+
+        # Run the command again with a warmed cache
+        output = self.run_command()
+        output_string = self.REAESC.sub("", output.read())
+        self.assertEqual(
+            output_string,
+            f"Successfully regenerated {total_renditions} image rendition(s)\n",
+        )

wagtail/images/tests/test_models.py

@@ -491,8 +491,8 @@ class TestRenditions(TestCase):
             },
         },
     )
-    def test_renditions_cache_backend(self):
-        cache = caches["renditions"]
+    def test_renditions_cache(self):
+        cache = Rendition.cache_backend
         rendition = self.image.get_rendition("width-500")
         rendition_cache_key = rendition.get_cache_key()
 
@@ -531,6 +531,29 @@ class TestRenditions(TestCase):
         new_rendition = self.image.get_rendition("width-500")
         self.assertFalse(hasattr(new_rendition, "_mark"))
 
+    def test_prefers_rendition_cache_backend(self):
+        with override_settings(
+            CACHES={
+                "default": {
+                    "BACKEND": "django.core.cache.backends.dummy.DummyCache",
+                },
+                "renditions": {
+                    "BACKEND": "django.core.cache.backends.dummy.DummyCache",
+                },
+            }
+        ):
+            self.assertEqual(Rendition.cache_backend, caches["renditions"])
+
+    def test_uses_default_cache_when_no_renditions_cache(self):
+        with override_settings(
+            CACHES={
+                "default": {
+                    "BACKEND": "django.core.cache.backends.dummy.DummyCache",
+                }
+            }
+        ):
+            self.assertEqual(Rendition.cache_backend, caches["default"])
+
     def test_focal_point(self):
         self.image.focal_point_x = 100
         self.image.focal_point_y = 200