diff --git a/src/libraries/turtle/constraint.hpp b/src/libraries/turtle/constraint.hpp
index 3912548..577f104 100644
--- a/src/libraries/turtle/constraint.hpp
+++ b/src/libraries/turtle/constraint.hpp
@@ -19,8 +19,6 @@ namespace mock
         {}
         Constraint f_;
     };
-    template< typename T, typename Constraint >
-    bool operator==( const T&, const constraint< Constraint >& );
 }
 
 #endif // #ifndef MOCK_CONSTRAINT_HPP_INCLUDED
diff --git a/src/libraries/turtle/expectation.hpp b/src/libraries/turtle/expectation.hpp
index 96afbae..63c0bc2 100644
--- a/src/libraries/turtle/expectation.hpp
+++ b/src/libraries/turtle/expectation.hpp
@@ -36,13 +36,6 @@ namespace detail
             , file_( "unknown location" )
             , line_( 0 )
         {}
-        virtual ~expectation_base()
-        {
-            for( sequences_cit it = sequences_.begin();
-                it != sequences_.end(); ++it )
-                (*it)->remove( this );
-        }
-
         void set_location( const std::string& file, int line )
         {
             file_ = file;
@@ -82,7 +75,12 @@ namespace detail
         }
 
     protected:
-        boost::shared_ptr< detail::invocation > i_;
+        ~expectation_base()
+        {
+            for( sequences_cit it = sequences_.begin();
+                it != sequences_.end(); ++it )
+                (*it)->remove( this );
+        }
 
         void expect( detail::invocation* i )
         {
@@ -95,6 +93,8 @@ namespace detail
             sequences_.push_back( s );
         }
 
+        boost::shared_ptr< detail::invocation > i_;
+
     private:
         typedef std::vector< boost::shared_ptr< detail::sequence_impl > > sequences_type;
         typedef sequences_type::const_iterator sequences_cit;
@@ -155,14 +155,14 @@ namespace detail
     public:
         bool is_valid() const
         {
-            return i_->is_valid();
+            return ! i_->exhausted();
         }
 
         MOCK_EXPECTATION_METHODS
 
         friend std::ostream& operator<<( std::ostream& s, const expectation& m )
         {
-            return s << (m.i_->is_valid() ? '.' : 'v') << ' ' << *m.i_;
+            return s << (m.i_->exhausted() ? 'v' : '.') << ' ' << *m.i_;
         }
     };
 
@@ -199,13 +199,13 @@ namespace detail
         } \
         bool is_valid( BOOST_PP_REPEAT_FROM_TO(0, n, MOCK_EXPECTATION_ARGS, BOOST_PP_EMPTY) ) const \
         { \
-            return i_->is_valid() \
+            return ! i_->exhausted() \
                 BOOST_PP_REPEAT_FROM_TO(0, n, MOCK_EXPECTATION_IS_VALID, BOOST_PP_EMPTY); \
         } \
         MOCK_EXPECTATION_METHODS \
         friend std::ostream& operator<<( std::ostream& s, const expectation& m ) \
         { \
-            return s << (m.i_->is_valid() ? '.' : 'v') << ' ' << *m.i_ << ".with( " \
+            return s << (m.i_->exhausted() ? 'v' : '.') << ' ' << *m.i_ << ".with( " \
                 << \
                 BOOST_PP_REPEAT_FROM_TO(0, n, MOCK_EXPECTATION_SERIALIZE, BOOST_PP_EMPTY) \
                 << " )"; \
diff --git a/src/libraries/turtle/invocation.hpp b/src/libraries/turtle/invocation.hpp
index f075320..24afefa 100644
--- a/src/libraries/turtle/invocation.hpp
+++ b/src/libraries/turtle/invocation.hpp
@@ -22,25 +22,14 @@ namespace detail
     {
     public:
         invocation() {}
-
         virtual ~invocation() {}
 
-        // Trigger invocation
-        // returns false if the invocation has failed
         virtual bool invoke() = 0;
-
-        // Test whether the invocation has been invoked or not
-        // returns true if the invocation has been invoked
-        virtual bool invoked() const = 0;
-
-        // Test whether the invocation is exhausted or not
-        // returns false if the invocation is exhausted
-        virtual bool is_valid() const = 0;
-
-        // Verify invocation
-        // returns false if the verification fails
         virtual bool verify() const = 0;
 
+        virtual bool invoked() const = 0;
+        virtual bool exhausted() const = 0;
+
         friend inline std::ostream& operator<<( std::ostream& s, const invocation& i )
         {
             return i.serialize( s );
@@ -75,9 +64,9 @@ namespace detail
             return count_ > 0;
         }
 
-        virtual bool is_valid() const
+        virtual bool exhausted() const
         {
-            return count_ < max_;
+            return count_ >= max_;
         }
 
         virtual bool verify() const
diff --git a/src/tests/turtle_test/invocation_test.cpp b/src/tests/turtle_test/invocation_test.cpp
index a85613e..aa1edda 100644
--- a/src/tests/turtle_test/invocation_test.cpp
+++ b/src/tests/turtle_test/invocation_test.cpp
@@ -16,10 +16,10 @@ BOOST_AUTO_TEST_CASE( unlimited )
 {
     mock::detail::unlimited invocation;
     BOOST_CHECK( invocation.verify() );
-    BOOST_CHECK( invocation.is_valid() );
+    BOOST_CHECK( ! invocation.exhausted() );
     BOOST_CHECK( invocation.invoke() );
     BOOST_CHECK( invocation.verify() );
-    BOOST_CHECK( invocation.is_valid() );
+    BOOST_CHECK( ! invocation.exhausted() );
     BOOST_CHECK( invocation.invoke() );
 }
 
@@ -27,10 +27,10 @@ BOOST_AUTO_TEST_CASE( once )
 {
     mock::detail::once invocation;
     BOOST_CHECK( ! invocation.verify() );
-    BOOST_CHECK( invocation.is_valid() );
+    BOOST_CHECK( ! invocation.exhausted() );
     BOOST_CHECK( invocation.invoke() );
     BOOST_CHECK( invocation.verify() );
-    BOOST_CHECK( ! invocation.is_valid() );
+    BOOST_CHECK( invocation.exhausted() );
     BOOST_CHECK( ! invocation.invoke() );
 }
 
@@ -38,7 +38,7 @@ BOOST_AUTO_TEST_CASE( never )
 {
     mock::detail::never invocation;
     BOOST_CHECK( invocation.verify() );
-    BOOST_CHECK( ! invocation.is_valid() );
+    BOOST_CHECK( invocation.exhausted() );
     BOOST_CHECK( ! invocation.invoke() );
 }
 
@@ -46,10 +46,10 @@ BOOST_AUTO_TEST_CASE( at_most )
 {
     mock::detail::at_most invocation( 1 );
     BOOST_CHECK( invocation.verify() );
-    BOOST_CHECK( invocation.is_valid() );
+    BOOST_CHECK( ! invocation.exhausted() );
     BOOST_CHECK( invocation.invoke() );
     BOOST_CHECK( invocation.verify() );
-    BOOST_CHECK( ! invocation.is_valid() );
+    BOOST_CHECK( invocation.exhausted() );
     BOOST_CHECK( ! invocation.invoke() );
 }
 
@@ -57,10 +57,10 @@ BOOST_AUTO_TEST_CASE( at_least )
 {
     mock::detail::at_least invocation( 1 );
     BOOST_CHECK( ! invocation.verify() );
-    BOOST_CHECK( invocation.is_valid() );
+    BOOST_CHECK( ! invocation.exhausted() );
     BOOST_CHECK( invocation.invoke() );
     BOOST_CHECK( invocation.verify() );
-    BOOST_CHECK( invocation.is_valid() );
+    BOOST_CHECK( ! invocation.exhausted() );
     BOOST_CHECK( invocation.invoke() );
 }
 
@@ -68,12 +68,12 @@ BOOST_AUTO_TEST_CASE( between )
 {
     mock::detail::between invocation( 1, 2 );
     BOOST_CHECK( ! invocation.verify() );
-    BOOST_CHECK( invocation.is_valid() );
+    BOOST_CHECK( ! invocation.exhausted() );
     BOOST_CHECK( invocation.invoke() );
     BOOST_CHECK( invocation.verify() );
-    BOOST_CHECK( invocation.is_valid() );
+    BOOST_CHECK( ! invocation.exhausted() );
     BOOST_CHECK( invocation.invoke() );
     BOOST_CHECK( invocation.verify() );
-    BOOST_CHECK( ! invocation.is_valid() );
+    BOOST_CHECK( invocation.exhausted() );
     BOOST_CHECK( ! invocation.invoke() );
 }