diff --git a/src/gui/model/tangible.cpp b/src/gui/model/tangible.cpp
index b2e5883a7..787006b78 100644
--- a/src/gui/model/tangible.cpp
+++ b/src/gui/model/tangible.cpp
@@ -33,6 +33,8 @@
 //#include "lib/symbol.hpp"
 //#include "include/logging.h"
 #include "gui/model/tangible.hpp"
+#include "gui/model/widget.hpp"
+#include "gui/model/controller.hpp"
 
 //#include <boost/noncopyable.hpp>
 //#include <string>
@@ -65,9 +67,8 @@ namespace model {
    * @param arguments suitable tuple of values, to be used to outfit the prototype
    */
   void
-  Tangible::prepareCommand (InvocationTrail const& prototype, Rec&& arguments)
+  Tangible::prepareCommand (Cmd const& prototype, Rec&& arguments)
   {
-    TODO ("invoke some hook for instrumentation?");
     uiBus_.act (prototype.bind(std::forward<Rec>(arguments)));
   }
   
@@ -78,10 +79,9 @@ namespace model {
    *        which needs to be outfitted with arguments and ready for invocation.
    */
   void
-  Tangible::issueCommand (InvocationTrail const& preparedAction)
+  Tangible::issueCommand (Cmd const& preparedAction)
   {
-    TODO ("invoke some hook for instrumentation?");
-    uiBus_.act (prototype.bang());
+    uiBus_.act (preparedAction.bang());
   }
   
   
diff --git a/src/gui/model/tangible.hpp b/src/gui/model/tangible.hpp
index d1044926c..eec3cbca5 100644
--- a/src/gui/model/tangible.hpp
+++ b/src/gui/model/tangible.hpp
@@ -68,14 +68,15 @@ namespace model {
     : boost::noncopyable
     {
     protected:
-      using interact::InvocationTrail;
-      using lib::diff::GenNode;
-      using lib::diff::Rec;
+      using GenNode = lib::diff::GenNode;
+      using Cmd = interact::InvocationTrail;
+      using Rec = lib::diff::Rec;
+      using ID = lib::idi::BareEntryID;
       
       ctrl::BusTerm uiBus_;
       
       
-      Tangible(EntryID identity, ctrl::BusTerm nexus)
+      Tangible(ID identity, ctrl::BusTerm& nexus)
         : uiBus_(nexus.attach(identity))
         { }
       
@@ -84,8 +85,8 @@ namespace model {
       
       void reset();
       
-      void prepareCommand (InvocationTrail const& prototype, Rec&& arguments);
-      void issueCommand (InvocationTrail const& preparedAction);
+      void prepareCommand (Cmd const& prototype, Rec&& arguments);
+      void issueCommand (Cmd const& preparedAction);
       
       void slotExpand();
       void slotReveal();
@@ -96,8 +97,14 @@ namespace model {
       void noteMark();
       
     protected:
-      virtual void doExpand()  =0;
-      virtual void doReveal()  =0;
+      virtual void doReset()  =0;
+      virtual void doExpand() =0;
+      virtual void doReveal() =0;
+      
+      virtual void doMsg()   =0;
+      virtual void doErr()   =0;
+      virtual void doFlash() =0;
+      virtual void doMark()  =0;
     private:
     };
   
diff --git a/tests/gui/abstract-tangible-test.cpp b/tests/gui/abstract-tangible-test.cpp
index 25301f911..55d934cbb 100644
--- a/tests/gui/abstract-tangible-test.cpp
+++ b/tests/gui/abstract-tangible-test.cpp
@@ -47,6 +47,7 @@
 
 #include "lib/test/run.hpp"
 #include "lib/test/test-helper.hpp"
+#include "test/mock-elm.hpp"
 #include "lib/error.hpp"
 //#include "gui/model/session-facade.hpp"
 //#include "gui/model/diagnostics.hpp"
@@ -64,7 +65,6 @@
 //using std::cout;
 //using std::endl;
 
-using lib::error::LUMIERA_ERROR_ASSERTION;
 
 
 namespace gui  {
diff --git a/tests/gui/test/mock-elm.hpp b/tests/gui/test/mock-elm.hpp
index 56967e595..967000497 100644
--- a/tests/gui/test/mock-elm.hpp
+++ b/tests/gui/test/mock-elm.hpp
@@ -47,14 +47,19 @@
 //#include "lib/util.hpp"
 #include "gui/model/tangible.hpp"
 #include "lib/diff/record.hpp"
+#include "test/nexus.hpp"
 
 //#include <boost/noncopyable.hpp>
 #include <string>
 
 
 namespace gui {
+  namespace error = lumiera::error;
+  using error::LUMIERA_ERROR_ASSERTION;
+  
 namespace test{
   
+  
 //  using lib::HashVal;
 //  using util::isnil;
   using lib::idi::EntryID;
@@ -79,28 +84,52 @@ namespace test{
       
       /* ==== Tangible interface ==== */
       
-      virtual void
-      act (GenNode command)  override
+      virtual void doReset()
         {
-          UNIMPLEMENTED ("");
+          UNIMPLEMENTED ("mock doReset");
         }
-      virtual void note (GenNode mark)     =0;
-      virtual void mark (GenNode mark)     =0;
       
-      virtual void act  (EntryID subject, GenNode command)  =0;
-      virtual void note (EntryID subject, GenNode mark)     =0;
-      virtual void mark (EntryID subject, GenNode mark)     =0;
+      virtual void doExpand()
+        {
+          UNIMPLEMENTED ("mock doExpand");
+        }
+      
+      virtual void doReveal()
+        {
+          UNIMPLEMENTED ("mock doReveal");
+        }
+      
+      virtual void doMsg()
+        {
+          UNIMPLEMENTED ("mock doMsg");
+        }
+      
+      virtual void doErr()
+        {
+          UNIMPLEMENTED ("mock doErr");
+        }
+      
+      virtual void doFlash()
+        {
+          UNIMPLEMENTED ("mock doFlash");
+        }
+      
+      virtual void doMark()
+        {
+          UNIMPLEMENTED ("mock doMark");
+        }
       
       
     protected:
     public:
       explicit
       MockElm(string id)
-        : gui::model::Tangible(TODO_generate_identity, TestNexus::hook())
+        : MockElm(EntryID<MockElm>(id))
         { }
       
       explicit
-      MockElm(EntryID identity, ctrl::BusTerm&& nexus =TestNexus::hook())
+      MockElm(ID identity, ctrl::BusTerm& nexus  =Nexus::testUI())
+        : gui::model::Tangible(identity, nexus)
         { }
     };