diff --git a/src/proc/mobject/session/query-focus-stack.hpp b/src/proc/mobject/session/query-focus-stack.hpp
index 7bac96683..d58b02481 100644
--- a/src/proc/mobject/session/query-focus-stack.hpp
+++ b/src/proc/mobject/session/query-focus-stack.hpp
@@ -112,6 +112,7 @@ namespace session {
   QueryFocusStack::clear ()
   {
     paths_.clear();
+    openDefaultFrame();
   }
   
   
diff --git a/src/proc/mobject/session/scope-path.hpp b/src/proc/mobject/session/scope-path.hpp
index b807e7ea0..d23d286cf 100644
--- a/src/proc/mobject/session/scope-path.hpp
+++ b/src/proc/mobject/session/scope-path.hpp
@@ -159,6 +159,7 @@ namespace session {
       /* == state diagnostics == */
       bool isValid()    const;
       bool empty()      const;
+      bool isRoot()     const;
       size_t size()     const;
       size_t length()   const;
       size_t ref_count()const;
@@ -267,6 +268,17 @@ namespace session {
     return path_.empty();
   }
   
+  inline bool
+  ScopePath::isRoot() const
+  {
+    return (1 == size())
+#if NOBUG_MODE_ALPHA
+        && path_[0].isRoot()
+#endif
+        ;
+  }
+  
+  
   
   /** @note actually this is an Lumiera Forward Iterator,
    *  yielding the path up to root as a sequence of
diff --git a/tests/43session.tests b/tests/43session.tests
index e70ae0af6..6f69b10b2 100644
--- a/tests/43session.tests
+++ b/tests/43session.tests
@@ -193,7 +193,8 @@ PLANNED "Query focus management" QueryFocus_test <<END
 END
 
 
-PLANNED "Query focus stack" QueryFocusStack_test <<END
+TEST "Query focus stack" QueryFocusStack_test <<END
+return: 0
 END
 
 
diff --git a/tests/components/proc/mobject/session/query-focus-stack-test.cpp b/tests/components/proc/mobject/session/query-focus-stack-test.cpp
index 844c08d31..109bea1f5 100644
--- a/tests/components/proc/mobject/session/query-focus-stack-test.cpp
+++ b/tests/components/proc/mobject/session/query-focus-stack-test.cpp
@@ -25,6 +25,7 @@
 #include "lib/test/test-helper.hpp"
 #include "proc/mobject/session/test-scopes.hpp"
 #include "proc/mobject/session/query-focus-stack.hpp"
+#include "proc/mobject/session/test-scope-invalid.hpp"
 #include "lib/util.hpp"
 
 
@@ -46,6 +47,9 @@ namespace test    {
    *       the stack frames (ScopePath instances) and cleans up unused frames.
    *       Similar to the ScopePath_test, we use a pseudo-session to create
    *       some path frames to play with.
+   * @note this test executes a lot of functionality in a manual by-hand way,
+   *       which in the actual application is accessed and utilised through
+   *       QueryFocus objects as frontend. 
    *       
    * @see  mobject::session::QueryFocusStack
    * @see  mobject::session::ScopePath
@@ -56,7 +60,8 @@ namespace test    {
       virtual void
       run (Arg) 
         {
-          // Prepare an (test)Index backing the PlacementRefs
+          // Prepare an (test)Index and
+          // set up dummy session contents
           PPIdx index = build_testScopes();
           
           createStack();
@@ -74,7 +79,7 @@ namespace test    {
           
           ASSERT (!isnil (stack));
           ASSERT (!isnil (stack.top()));
-          ASSERT (stack.top().getLeaf().isRoot());
+          ASSERT (stack.top().isRoot());
         }
       
       
@@ -106,7 +111,7 @@ namespace test    {
           
           // can use/navigate the stack top frame
           stack.top().goRoot();
-          ASSERT (isnil (stack.top())); // now indeed at root == empty path
+          ASSERT (!stack.top()); // now indeed at root == no path
           ASSERT (secondFrame.getLeaf().isRoot());
           ASSERT (secondFrame == stack.top());
           
@@ -155,7 +160,7 @@ namespace test    {
           ScopePath& anotherFrame = stack.push(startPoint);
           ASSERT (0 == anotherFrame.ref_count());
           ASSERT (1 == firstFrame.ref_count());
-          intrusive_ptr_release (&anotherFrame);
+          intrusive_ptr_release (&firstFrame);
           ASSERT (0 == firstFrame.ref_count());
           ASSERT (firstFrame.getLeaf() == startPoint);
           
@@ -188,16 +193,16 @@ namespace test    {
           intrusive_ptr_add_ref (&firstFrame);
           
           ScopePath beforeInvalidNavigation = firstFrame;
-          Scope unrelatedScope (TestPlacement<> (*new DummyMO));
+          Scope const& unrelatedScope = fabricate_invalidScope();
           
           // try to navigate to an invalid place
-          VERIFY_ERROR (INVALID, stack.top().navigate (unrelatedScope) );
+          VERIFY_ERROR (INVALID_SCOPE, stack.top().navigate (unrelatedScope) );
           ASSERT (1 == stack.size());
           ASSERT (1 == firstFrame.ref_count());
           ASSERT (stack.top().getLeaf() == startPoint);
           
           // try to push an invalid place
-          VERIFY_ERROR (INVALID, stack.push (unrelatedScope) );
+          VERIFY_ERROR (INVALID_SCOPE, stack.push (unrelatedScope) );
           ASSERT (1 == stack.size());
           ASSERT (1 == firstFrame.ref_count());
           ASSERT (stack.top().getLeaf() == startPoint);
diff --git a/tests/components/proc/mobject/session/scope-path-test.cpp b/tests/components/proc/mobject/session/scope-path-test.cpp
index 30cc7fc92..d425e394c 100644
--- a/tests/components/proc/mobject/session/scope-path-test.cpp
+++ b/tests/components/proc/mobject/session/scope-path-test.cpp
@@ -26,6 +26,7 @@
 #include "proc/mobject/session/test-scopes.hpp"
 #include "proc/mobject/session/placement-index.hpp"
 #include "proc/mobject/session/scope-path.hpp"
+#include "proc/mobject/session/test-scope-invalid.hpp"
 #include "lib/util.hpp"
 
 
@@ -41,30 +42,6 @@ namespace test    {
   using lumiera::error::LUMIERA_ERROR_INVALID;
   
   
-  namespace { // subversive test helper...
-    
-    Scope const&
-    fabricate_invalidScope()
-    {        /** 
-              * assumed to have identical memory layout
-              * to a Scope object, as the latter is implemented
-              * by a PlacementRef, which in turn is just an
-              * encapsulated Placement-ID
-              */
-             struct Ambush
-               {
-                 /** random ID assumed to be
-                  *  nowhere in the model */
-                 PlacementMO::ID derailed_;
-               };
-      
-      static Ambush _kinky_;
-      return *reinterpret_cast<Scope*> (&_kinky_);
-    }
-  }
-  
-  
-  
   
   
   /***************************************************************************
diff --git a/tests/components/proc/mobject/session/test-scope-invalid.hpp b/tests/components/proc/mobject/session/test-scope-invalid.hpp
new file mode 100644
index 000000000..ecfa18f04
--- /dev/null
+++ b/tests/components/proc/mobject/session/test-scope-invalid.hpp
@@ -0,0 +1,63 @@
+/*
+  TEST-SCOPE-INVALID.hpp  -  helper for placement scope and scope stack tests
+ 
+  Copyright (C)         Lumiera.org
+    2010,               Hermann Vosseler <Ichthyostega@web.de>
+ 
+  This program is free software; you can redistribute it and/or
+  modify it under the terms of the GNU General Public License as
+  published by the Free Software Foundation; either version 2 of the
+  License, or (at your option) any later version.
+ 
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+ 
+  You should have received a copy of the GNU General Public License
+  along with this program; if not, write to the Free Software
+  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ 
+*/
+
+
+#ifndef MOBJECT_SESSION_TEST_SCOPE_INVALID_H
+#define MOBJECT_SESSION_TEST_SCOPE_INVALID_H
+
+
+#include "proc/mobject/placement.hpp"
+#include "proc/mobject/session/scope.hpp"
+
+
+
+namespace mobject {
+namespace session {
+namespace test    {
+  
+  
+  namespace { // nifty subversive test helper...
+    
+    Scope const&
+    fabricate_invalidScope()
+    {        /** 
+              * assumed to have identical memory layout
+              * to a Scope object, as the latter is implemented
+              * by a PlacementRef, which in turn is just an
+              * encapsulated Placement-ID
+              */
+             struct Ambush
+               {
+                 /** random ID assumed to be
+                  *  nowhere in the model */
+                 PlacementMO::ID derailed_;
+               };
+      
+      static Ambush _kinky_;
+      return *reinterpret_cast<Scope*> (&_kinky_);
+    }
+  }
+  
+  
+  
+}}} // namespace mobject::session::test
+#endif