rib: Unit tests for RibManager

Change-Id: I8096089f6cc8a6eea7be51278b29700c79e68d5c
Refs: #1501
diff --git a/rib/rib-manager.hpp b/rib/rib-manager.hpp
index f664528..6566d1f 100644
--- a/rib/rib-manager.hpp
+++ b/rib/rib-manager.hpp
@@ -56,7 +56,8 @@
     }
   };
 
-  RibManager();
+  explicit
+  RibManager(ndn::Face& face);
 
   void
   registerWithNfd();
@@ -199,7 +200,7 @@
 
 private:
   Rib m_managedRib;
-  ndn::Face m_face;
+  ndn::Face& m_face;
   ndn::nfd::Controller m_nfdController;
   ndn::KeyChain m_keyChain;
   ndn::ValidatorConfig m_localhostValidator;