Fix BufferedPersister.

lib/valkyrie/persistence/delete_tracking_buffer.rb

@@ -24,6 +24,12 @@ def delete(resource:)
         @deletes << resource
         super
       end
+
+      # A buffered memory persister can save anything, it doesn't have to hold
+      # a consistent internal state.
+      def valid_for_save?(_)
+        true
+      end
     end
   end
 end

spec/valkyrie/persistence/buffered_persister_spec.rb

@@ -30,5 +30,15 @@ class Resource < Valkyrie::Resource
       end
       expect(buffer.query_service.find_all.length).to eq 1
     end
+    it "can handle saving an object which was previously saved" do
+      buffer = nil
+      resource = Resource.new
+      output = adapter.persister.save(resource: resource)
+      persister.with_buffer do |inner_persister, memory_buffer|
+        inner_persister.save(resource: output)
+        buffer = memory_buffer
+      end
+      expect(buffer.query_service.find_all.length).to eq 1
+    end
   end
 end