Improve cache testing

django_large_image/cache.py

@@ -10,12 +10,13 @@
 class DjangoCache(BaseCache):
     """Use Django cache as the backing cache for large-image."""
 
-    def __init__(self, cache, getsizeof=None):
+    def __init__(self, cache, alias, getsizeof=None):
         super().__init__(0, getsizeof=getsizeof)
         self._django_cache = cache
+        self._alias = alias
 
     def __repr__(self):  # pragma: no cover
-        return f'DjangoCache<{repr(self._django_cache._alias)}>'
+        return f'DjangoCache<{repr(self._alias)}>'
 
     def __iter__(self):  # pragma: no cover
         # return invalid iter
@@ -65,8 +66,8 @@ def getCache():  # noqa: N802
         try:
             name = getattr(settings, 'LARGE_IMAGE_CACHE_NAME', 'default')
             dajngo_cache = caches[name]
-        except ImproperlyConfigured:
+        except ImproperlyConfigured:  # pragma: no cover
             raise TileCacheConfigurationError
         cache_lock = threading.Lock()
-        cache = DjangoCache(dajngo_cache)
+        cache = DjangoCache(dajngo_cache, alias=name)
         return cache, cache_lock

project/example/core/tests/test_cache.py

@@ -1,36 +1,57 @@
+from contextlib import contextmanager
+
 from large_image.cache_util.base import BaseCache
 import pytest
 
 from django_large_image import tilesource
 from django_large_image.cache import DjangoCache
 
 
-@pytest.fixture
-def cache_miss_counter():
+@contextmanager
+def cache_tracker():
+    cache, _ = DjangoCache.getCache()
+    cache.clear()
+
     class Counter:
         def __init__(self):
-            self.count = 0
+            self.reset()
+            self.cache = cache
 
         def reset(self):
             self.count = 0
+            self.keys = set()
 
     counter = Counter()
 
-    def missing(*args, **kwargs):
+    def missing(self, key, *args, **kwargs):
         counter.count += 1
-        BaseCache.__missing__(*args, **kwargs)
+        counter.keys.add(key)
+        BaseCache.__missing__(self, key, *args, **kwargs)
 
     original = DjangoCache.__missing__
     DjangoCache.__missing__ = missing
     yield counter
     DjangoCache.__missing__ = original
 
 
-def test_tile(geotiff_path, cache_miss_counter):
+def test_cache_tile(geotiff_path):
+    source = tilesource.get_tilesource_from_path(geotiff_path)
+    with cache_tracker() as tracker:
+        _ = source.getTile(0, 0, 0, encoding='PNG')
+        assert tracker.count == 1
+        _ = source.getTile(0, 0, 0, encoding='PNG')
+        assert tracker.count == 1
+
+
+def test_cache_access(geotiff_path):
     source = tilesource.get_tilesource_from_path(geotiff_path)
-    cache_miss_counter.reset()
-    # Check size of cache
-    _ = source.getTile(0, 0, 0, encoding='PNG')
-    assert cache_miss_counter.count == 1
-    _ = source.getTile(0, 0, 0, encoding='PNG')
-    assert cache_miss_counter.count == 1
+    with cache_tracker() as tracker:
+        _ = source.getTile(0, 0, 0, encoding='PNG')
+        assert tracker.count == 1
+        assert all([k in tracker.cache for k in tracker.keys])
+        for k in tracker.keys:
+            del tracker.cache[k]
+        assert all([k not in tracker.cache for k in tracker.keys])
+        _ = source.getTile(0, 0, 0, encoding='PNG')
+        assert tracker.count == 2
+        assert len(tracker.keys) == 1