Add new unit test and fix implementation

lib/octopus/model.rb

@@ -19,6 +19,7 @@ def using(shard)
         end
 
         if Octopus.enabled?
+          self.connection_proxy.current_shard_dirty = true
           Octopus::ScopeProxy.new(shard, self)
         else
           self

lib/octopus/scope_proxy.rb

@@ -23,6 +23,7 @@ def initialize(shard, klass)
     def using(shard)
       fail "Nonexistent Shard Name: #{shard}" if @klass.connection.shards[shard].nil?
       @current_shard = shard
+      @klass.connection_proxy.current_shard_dirty = true
       self
     end
 
@@ -37,7 +38,6 @@ def connection
       if @klass.custom_octopus_connection && @klass.allowed_shard?(@current_shard)
         # Force use of proxy, given we called 'using' explicitly to get here
         @klass.connection_proxy.current_model = @klass
-        @klass.connection_proxy.current_shard_dirty = true
         @klass.connection_proxy
       else
         @klass.connection

spec/octopus/octopus_spec.rb

@@ -106,6 +106,14 @@
       end
     end
 
+    it 'sends queries to master when forced to use master' do
+      OctopusHelper.using_environment :production_replicated do
+        Octopus.fully_replicated do
+          expect(User.using(:master).count).to eq(0)
+        end
+      end
+    end
+
     it 'allows nesting' do
       OctopusHelper.using_environment :production_replicated do
         Octopus.fully_replicated do