Update src/Middleware/OutputCaching/test/MemoryOutputCacheStoreTests.cs

Co-authored-by: Rick Anderson <[email protected]>

src/Middleware/OutputCaching/test/MemoryOutputCacheStoreTests.cs

@@ -210,7 +210,7 @@ public async Task ReplacedEntries_AreNotRemovedFromTags()
 
         testClock.Advance(TimeSpan.FromMilliseconds(10));
 
-        // Background expiration checks are triggered by misc cache activity.
+        // Trigger background expiration by accessing the cache.
         _ = cache.Get("a");
 
         var resulta = await store.GetAsync("a", default);