Fixed some unit tests by cleaning up resources properly.

src/drc/drc/built-in-macros/drc.lym

@@ -3800,6 +3800,12 @@ CODE
 
     end
     
+    def _finish
+      clear_connections
+      # cleans up the L2N object
+      modified
+    end
+
   private
 
     def modified
@@ -4996,6 +5002,7 @@ CODE
 
       # clean up temp data
       @dss && @dss._destroy
+      @netter && @netter._finish
       
       if final && @log_file
         @log_file.close