2 files changed, 34 insertions, 6 deletions
diff --git a/activesupport/test/cache/stores/mem_cache_store_test.rb b/activesupport/test/cache/stores/mem_cache_store_test.rb
index ccb3b7403f..3e2316f217 100644
--- a/activesupport/test/cache/stores/mem_cache_store_test.rb
+++ b/activesupport/test/cache/stores/mem_cache_store_test.rb
@@ -17,6 +17,12 @@ class SlowDalliClient < Dalli::Client
   end
 end
 
+class UnavailableDalliServer < Dalli::Server
+  def alive?
+    false
+  end
+end
+
 class MemCacheStoreTest < ActiveSupport::TestCase
   begin
     ss = Dalli::Client.new("localhost:11211").stats
@@ -46,6 +52,7 @@ class MemCacheStoreTest < ActiveSupport::TestCase
   include EncodedKeyCacheBehavior
   include AutoloadingCacheBehavior
   include ConnectionPoolBehavior
+  include FailureSafetyBehavior
 
   def test_raw_values
     cache = ActiveSupport::Cache.lookup_store(:mem_cache_store, raw: true)
@@ -118,4 +125,14 @@ class MemCacheStoreTest < ActiveSupport::TestCase
       Dalli.send(:remove_const, :Client)
       Dalli.const_set(:Client, old_client)
     end
+
+    def emulating_unavailability
+      old_server = Dalli.send(:remove_const, :Server)
+      Dalli.const_set(:Server, UnavailableDalliServer)
+
+      yield ActiveSupport::Cache::MemCacheStore.new
+    ensure
+      Dalli.send(:remove_const, :Server)
+      Dalli.const_set(:Server, old_server)
+    end
 end
diff --git a/activesupport/test/cache/stores/redis_cache_store_test.rb b/activesupport/test/cache/stores/redis_cache_store_test.rb
index cdbb5dc4c6..7c1286a115 100644
--- a/activesupport/test/cache/stores/redis_cache_store_test.rb
+++ b/activesupport/test/cache/stores/redis_cache_store_test.rb
@@ -156,15 +156,26 @@ module ActiveSupport::Cache::RedisCacheStoreTests
   class StoreAPITest < StoreTest
   end
 
-  class FailureSafetyTest < StoreTest
-    test "fetch read failure returns nil" do
+  class UnavailableRedisClient < Redis::Client
+    def ensure_connected
+      raise Redis::BaseConnectionError
     end
+  end
 
-    test "fetch read failure does not attempt to write" do
-    end
+  class FailureSafetyTest < StoreTest
+    include FailureSafetyBehavior
 
-    test "write failure returns nil" do
-    end
+    private
+
+      def emulating_unavailability
+        old_client = Redis.send(:remove_const, :Client)
+        Redis.const_set(:Client, UnavailableRedisClient)
+
+        yield ActiveSupport::Cache::RedisCacheStore.new
+      ensure
+        Redis.send(:remove_const, :Client)
+        Redis.const_set(:Client, old_client)
+      end
   end
 
   class DeleteMatchedTest < StoreTest