diff --git a/YASI_12/YASI_12.vcxproj b/YASI_12/YASI_12.vcxproj
index ae46f3d..ad1e614 100644
--- a/YASI_12/YASI_12.vcxproj
+++ b/YASI_12/YASI_12.vcxproj
@@ -92,7 +92,7 @@
     <ClInclude Include="ds.iterator.h">
       <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">false</ExcludedFromBuild>
     </ClInclude>
-    <ClInclude Include="ds.iterator_test.h" />
+    <ClInclude Include="ds.iterator.test.h" />
     <ClInclude Include="ds.kvpair.h" />
     <ClInclude Include="ds.LinearProbingHashTable.h" />
     <ClInclude Include="ds.list.h" />
@@ -106,7 +106,9 @@
       <ExcludedFromBuild Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">true</ExcludedFromBuild>
     </ClInclude>
     <ClInclude Include="test.h" />
+    <ClInclude Include="test.this.module.h" />
     <ClInclude Include="utils.h" />
+    <ClInclude Include="utils.test.h" />
   </ItemGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">
diff --git a/YASI_12/YASI_12.vcxproj.filters b/YASI_12/YASI_12.vcxproj.filters
index 445f702..c1f9f23 100644
--- a/YASI_12/YASI_12.vcxproj.filters
+++ b/YASI_12/YASI_12.vcxproj.filters
@@ -104,9 +104,6 @@
     <ClInclude Include="ds.iterator.h">
       <Filter>Header Files\Common</Filter>
     </ClInclude>
-    <ClInclude Include="ds.iterator_test.h">
-      <Filter>Header Files\Common</Filter>
-    </ClInclude>
     <ClInclude Include="ds.kvpair.h">
       <Filter>Header Files\Common</Filter>
     </ClInclude>
@@ -143,5 +140,14 @@
     <ClInclude Include="alg.graph.h">
       <Filter>Header Files\Algorithms</Filter>
     </ClInclude>
+    <ClInclude Include="ds.iterator.test.h">
+      <Filter>Header Files\Common</Filter>
+    </ClInclude>
+    <ClInclude Include="test.this.module.h">
+      <Filter>Header Files\Common</Filter>
+    </ClInclude>
+    <ClInclude Include="utils.test.h">
+      <Filter>Header Files\Common</Filter>
+    </ClInclude>
   </ItemGroup>
 </Project>
\ No newline at end of file
diff --git a/YASI_12/common.h b/YASI_12/common.h
index 831c447..02a6a7a 100644
--- a/YASI_12/common.h
+++ b/YASI_12/common.h
@@ -25,7 +25,14 @@
 #define DETECT_MEM_LEAKS()	
 
 #endif // _WIN32
+
+
 #include <cassert>
+
+/*--------- Availability of Google C++ Test Framework ----------*/
+
+// whether using  Google C++ Test Framework
+#define GTEST	1
 #include "test.h"
 
 
diff --git a/YASI_12/ds.iterator.h b/YASI_12/ds.iterator.h
index 6ce732b..f5c3f8d 100644
--- a/YASI_12/ds.iterator.h
+++ b/YASI_12/ds.iterator.h
@@ -2,10 +2,13 @@
 #include "common.h"
 #include "utils.h"
 #include "ds.node.h"
-#include "test.h"
 
 using namespace std;
 
+/******** enable-disable testing *******/
+#include "test.this.module.h"
+
+
 namespace yasi{
 	namespace ds{
 
@@ -14,7 +17,7 @@ namespace yasi{
 					class Iterator >
 		class IteratorBase{
 			////////////////// enable testing ////////////////
-			friend class IteratorTest;
+			FRIEND_TEST_CLASS(IteratorTest);
 
 			typedef IteratorBase<Elem,Iterated,Iterator> self;
 		protected:
@@ -44,7 +47,7 @@ namespace yasi{
 					class Iterator >
 		class ForwardIterator :public virtual IteratorBase<E,Iterated,Iterator>{
 			////////////////// enable testing ////////////////
-			friend class IteratorTest;
+			FRIEND_TEST_CLASS(IteratorTest);
 
 			typedef IteratorBase<E, Iterated, Iterator> base;
 			typedef ForwardIterator<E,Iterated,Iterator> self;
@@ -67,7 +70,7 @@ namespace yasi{
 					class Iterator>
 		class BackwardIterator :public virtual IteratorBase<E,Iterated,Iterator>{
 			////////////////// enable testing ////////////////
-			friend class IteratorTest;
+			FRIEND_TEST_CLASS(IteratorTest);
 
 			typedef IteratorBase<E, Iterated, Iterator> base;
 			typedef BackwardIterator<E, Iterated, Iterator> self;
@@ -94,7 +97,7 @@ namespace yasi{
 				public virtual ForwardIterator<E, Iterated, Iterator>,
 				public virtual BackwardIterator<E, Iterated, Iterator>{
 			////////////////// enable testing ////////////////
-			friend class IteratorTest;
+			FRIEND_TEST_CLASS(IteratorTest);
 
 			typedef ForwardIterator<E, Iterated, Iterator> base1;
 			typedef BackwardIterator<E, Iterated, Iterator> base2;
@@ -115,7 +118,7 @@ namespace yasi{
 		template<class E, class Node, class Iterator>
 		class NodeIteratorBase : public virtual ForwardIterator<E, Node, Iterator>{
 			////////////////// enable testing ////////////////
-			friend class IteratorTest;
+			FRIEND_TEST_CLASS(IteratorTest);
 
 			typedef ForwardIterator<E, Node, Iterator> base;
 			typedef NodeIteratorBase<E,Node,Iterator> self;
@@ -137,7 +140,7 @@ namespace yasi{
 		template<class E, class Node, class Iterator > // E is the value type
 		class ForwardNodeIterator : public NodeIteratorBase<E, Node,Iterator >{
 			////////////////// enable testing ////////////////
-			friend class IteratorTest;
+			FRIEND_TEST_CLASS(IteratorTest);
 
 			typedef NodeIteratorBase<E, Node, Iterator > base;
 			typedef ForwardNodeIterator<E, Node, Iterator> self;
@@ -152,7 +155,11 @@ namespace yasi{
 			// operators
 			//virtual E& operator* () const { return pNode->element; };
 			self& operator = (const self& other){ this->pNode = other.pNode; return *this; }
-			self operator ++ (int){ self temp(this->pNode); incr();  return temp; }
+			self operator ++ (int){ 
+				self temp(this->pNode); 
+				incr();  
+				return temp; 
+			}
 			self& operator ++ (){ incr();  return *this; }
 		};
 
@@ -163,6 +170,9 @@ namespace yasi{
 			public virtual NodeIteratorBase<E, Node, Iterator >, 
 			public virtual BidirectionalIterator<E,Node, Iterator>{
 
+			////////////////// enable testing ////////////////
+			FRIEND_TEST_CLASS(IteratorTest);
+
 			typedef NodeIteratorBase<E, Node, Iterator > base;
 			typedef ForwardIterator<E, Node, Iterator > base1; // for virtual inheritance
 			typedef BackwardIterator<E, Node, Iterator > base2; // for virtual inheritance
diff --git a/YASI_12/ds.iterator_test.h b/YASI_12/ds.iterator.test.h
similarity index 55%
rename from YASI_12/ds.iterator_test.h
rename to YASI_12/ds.iterator.test.h
index 1a0dd58..fafe2e5 100644
--- a/YASI_12/ds.iterator_test.h
+++ b/YASI_12/ds.iterator.test.h
@@ -1,11 +1,13 @@
 #pragma once
 #include "ds.iterator.h"
-#include "ds.node.h"
 using namespace std;
 
 namespace yasi{
 	namespace ds{
+
 		///////////////// test ///////////////
+#if GTEST && YASI_TEST_THIS_MODULE
+
 		class IteratorTest :public yasi::Test{
 			
 			// derive from forward node iterator
@@ -14,7 +16,7 @@ namespace yasi{
 				typedef ForwardNodeIterator < E, Node, ForwardNodeIteratorDerived<E, Node> > base;
 			public:
 				virtual ~ForwardNodeIteratorDerived(){}
-				ForwardNodeIteratorDerived(Node* pNode) : base(pNode){}
+				ForwardNodeIteratorDerived(Node* pNode) : base(pNode), IteratorBase(pNode){}
 			};
 
 		public:
@@ -31,20 +33,36 @@ namespace yasi{
 
 				// create iterator
 				Iterator it(n[0]);
+				Node* node;
 				int i = 0;
 				do{
-					ASSERT_EQ(it.pNode, n[i]) << "wrong iterator node at i=" << i;
-					ASSERT_EQ(*it, i) << "wrong iterator value at i=" << i;
-					ASSERT_EQ(it.pNode, (it++).pNode) << "wrong postfix increment at i=" << i;
-					ASSERT_EQ(it.pNode->next(), (++it).pNode) << "wrong postfix increment at i=" << i;
-					// it already incremente
+					Iterator tempIter = it;
+					// dereference
+					ASSERT_EQ(*tempIter, i) << "wrong iterator value at i=" << i;
+					ASSERT_EQ(tempIter.pNode, n[i]) << "wrong iterator node at i=" << i;
+					// postfix++
+					node = tempIter.pNode;
+					ASSERT_EQ(node, (tempIter++).pNode) << "wrong postfix increment at i=" << i;
+					// prefix++
+					tempIter = it;
+					node = tempIter.pNode->next();
+					ASSERT_EQ(node, (++tempIter).pNode) << "wrong prefix increment at i=" << i;
+					// next iteration
 					i++;
+					it++;
 				} while (it.pNode != NULL);
-				ASSERT_EQ(11, i) << "i not 11";
+				ASSERT_EQ(10, i) << "i not 10";
+
+				// cleanup
+				for (int i = 0; i < 10; i++){
+					DELETE_SAFE(n[i]);
+				}
 			}
 		};
 
 		ADD_TEST_F(IteratorTest, forwardNodeIterator);
 
+#endif // GTEST  && YASI_TEST_THIS_MODULE
+
 	}
 }
\ No newline at end of file
diff --git a/YASI_12/ds.node.h b/YASI_12/ds.node.h
index 3d7d65b..fb44089 100644
--- a/YASI_12/ds.node.h
+++ b/YASI_12/ds.node.h
@@ -55,7 +55,7 @@ namespace yasi{
 			typedef SListNode<E> self;
 		public:
 			SListNode(){}
-			SListNode(const E& elem) : base(elem){}
+			SListNode(const E& elem) : base(elem), NodeBase<E>(elem){}
 			/////////////////////////////////////
 			//// very important: since we are doing virtual inheritance,
 			//// we need to specify all vertual constructors in the initializer list
diff --git a/YASI_12/main.cpp b/YASI_12/main.cpp
index 30f4fe3..86828c6 100644
--- a/YASI_12/main.cpp
+++ b/YASI_12/main.cpp
@@ -1,19 +1,19 @@
 #include "common.h"
-#include "utils.h"
-#include "ds.singlylinkedlist.h"
-#include "ds.doublylinkedlist.h"
-#include "ds.arraybinarytree.h"
-#include "ds.binaryheap.h"
-#include "ds.binarytree.h"
-#include "ds.binarysearchtree.h"
-#include "ds.priorityqueue.h"
-#include "ds.BSTDictionary.h"
-#include "ds.separatechaininghashtable.h"
-#include "ds.intlinearprobinghashtable.h"
-#include "ds.linearprobinghashtable.h"
-#include "ds.hopscotchhashtable.h"
-#include "ds.graph.h"
-#include "alg.graph.h"
+//#include "utils.h"
+//#include "ds.singlylinkedlist.h"
+//#include "ds.doublylinkedlist.h"
+//#include "ds.arraybinarytree.h"
+//#include "ds.binaryheap.h"
+//#include "ds.binarytree.h"
+//#include "ds.binarysearchtree.h"
+//#include "ds.priorityqueue.h"
+//#include "ds.BSTDictionary.h"
+//#include "ds.separatechaininghashtable.h"
+//#include "ds.intlinearprobinghashtable.h"
+//#include "ds.linearprobinghashtable.h"
+//#include "ds.hopscotchhashtable.h"
+//#include "ds.graph.h"
+//#include "alg.graph.h"
 
 //#include "Sorter.h"
 
@@ -26,23 +26,34 @@
 using namespace yasi;
 using namespace std;
 
-void testSort();
+/*------------- Testing ---------------*/
+#define YASI_TEST_THIS_MODULE 1
+#include "utils.test.h"
+#include "ds.iterator.test.h"
+
+int testAll(int* argc, char** argv){
 
-int main(int argc, char** argv){
-	
 	// currently only supported on Windows systems
 	DETECT_MEM_LEAKS();
 
-	::testing::InitGoogleTest(&argc, argv); // init google test
+	::testing::InitGoogleTest(argc, argv); // init google test
 
 	int retVal = RUN_ALL_TESTS(); // run all test cases
 
+	return retVal;
+}
+
+int main(int argc, char** argv){
+	
+	// currently only supported on Windows systems
+	DETECT_MEM_LEAKS();
+
+	int retVal = testAll(& argc, argv);
+
 	cout << endl;
 	cout << "Press any key..." << endl;
 	getchar();
 	return retVal;
-	//testSort();
-	//testArrayBinaryTree();
 }
 
 
diff --git a/YASI_12/test.h b/YASI_12/test.h
index 5a2ad18..62e992f 100644
--- a/YASI_12/test.h
+++ b/YASI_12/test.h
@@ -1,4 +1,8 @@
 #pragma once
+
+// available only if Google C++ Test Framework is available
+#if GTEST
+
 #include "gtest\gtest.h"
 
 namespace yasi{
@@ -30,4 +34,6 @@ namespace yasi{
 	public:
 		virtual ~Test(){}
 	};
-}
+} // namespace yasi
+
+#endif // GTEST
diff --git a/YASI_12/test.this.module.h b/YASI_12/test.this.module.h
new file mode 100644
index 0000000..2fa5b6e
--- /dev/null
+++ b/YASI_12/test.this.module.h
@@ -0,0 +1,23 @@
+// deliberately not using #pragma once
+
+// Are we required to test classes defined in this file?
+#if YASI_TEST_THIS_MODULE
+
+#if GTEST
+
+#define FRIEND_TEST_CLASS(className)	\
+	friend class className
+
+#else // GTEST
+// GTest not available
+#define FRIEND_TEST_CLASS(className)	
+
+#endif // GTEST
+
+#else // YASI_TEST_THIS_MODULE
+
+// We don't want to test classes defined in this file
+#define FRIEND_TEST_CLASS(className)	
+
+
+#endif // YASI_TEST_THIS_MODULE
\ No newline at end of file
diff --git a/YASI_12/utils.h b/YASI_12/utils.h
index 9ae4a17..726bfc1 100644
--- a/YASI_12/utils.h
+++ b/YASI_12/utils.h
@@ -7,6 +7,9 @@
 #include <string>
 using namespace std;
 
+/****** enable-disable testing classes in this file ******/
+#include "test.this.module.h"
+
 namespace yasi{
 
 // compares two arrays
@@ -155,73 +158,5 @@ typename enable_if<!has_to_string<T,
 
 */
 
-////////////////////////////////
-///// test //////////////////////
-/////////////////////////////////
-
-class UtilsTest : public Test{
-public:
-	void whichPowerOfTwo_(){
-		ASSERT_EQ(0, whichPowerOfTwo(1));
-		ASSERT_EQ(1, whichPowerOfTwo(2));
-		ASSERT_EQ(2, whichPowerOfTwo(4));
-		ASSERT_EQ(4, whichPowerOfTwo(16));
-		ASSERT_EQ(-1, whichPowerOfTwo(0));
-		ASSERT_EQ(-1, whichPowerOfTwo(-5));
-		ASSERT_EQ(-1, whichPowerOfTwo(7));
-	}
-	void arrrev(){
-		// regular
-		int srcArr[] = { 10, 20, 30 }; // odd number of entries
-		int destArr[] = { 30, 20, 10 };
-		int* pRev = new int[3];
-		yasi::arrrev(srcArr, 3, &pRev);
-		ASSERT_NE(0, (int)pRev) << "reversed array is NULL";
-		for (int i = 0; i < 3; i++){
-			ASSERT_EQ(destArr[i], pRev[i]) << "element mismatch at reverse index " << i;
-		}
-		DELETE_ARR_SAFE(pRev);
-
-		int srcArr2[] = { 10, 20, 30, 40 }; // even number of entries
-		int destArr2[] = { 40, 30, 20, 10 };
-		pRev = new int[4];
-		yasi::arrrev(srcArr2, 4, &pRev);
-		ASSERT_NE(0, (int)pRev) << "reversed array is NULL";
-		for (int i = 0; i < 4; i++){
-			ASSERT_EQ(destArr2[i], pRev[i]) << "element mismatch at reverse index " << i;
-		}
-		DELETE_ARR_SAFE(pRev);
-		
-		// bad input
-		int* pNull = NULL;
-		yasi::arrrev(pNull, 3, &pRev);
-		ASSERT_EQ(0, (int)pRev) << "worked on a NULL pointer";
-		yasi::arrrev(srcArr, 0, &pRev);
-		ASSERT_EQ(0, (int)pRev) << "worked on zero size";
-		DELETE_ARR_SAFE(pRev);
-		yasi::arrrev(srcArr, -1, &pRev);
-		ASSERT_EQ(0, (int)pRev) << "worked on negativesize";
-		//DELETE_ARR_SAFE(pRev);
-	}
-	void strPurge(){
-		string str = "abedabecaebc";
-
-		// purge chars present
-		string str2 = yasi::strPurge(str, "de");
-		ASSERT_EQ("ababcabc", str2) << "failed";
-
-		// purge chars absent
-		str2 = yasi::strPurge(str, "x");
-		ASSERT_EQ(str, str2) << "failed";
-
-		// no chars given
-		str2 = yasi::strPurge(str, "");
-		ASSERT_EQ(str, str2) << "failed";
-	}
-};
-
-ADD_TEST_F(UtilsTest, arrrev);
-ADD_TEST_F(UtilsTest, strPurge);
-ADD_TEST_F(UtilsTest, whichPowerOfTwo_);
 
 } // namespace yasi
\ No newline at end of file
diff --git a/YASI_12/utils.test.h b/YASI_12/utils.test.h
new file mode 100644
index 0000000..405290e
--- /dev/null
+++ b/YASI_12/utils.test.h
@@ -0,0 +1,79 @@
+#pragma once
+#include "common.h"
+#include "utils.h"
+
+////////////////////////////////
+///////// Test utils.h /////////
+/////////////////////////////////
+
+namespace yasi{
+
+#if GTEST && YASI_TEST_THIS_MODULE
+	class UtilsTest : public Test{
+	public:
+		void whichPowerOfTwo_(){
+			ASSERT_EQ(0, whichPowerOfTwo(1));
+			ASSERT_EQ(1, whichPowerOfTwo(2));
+			ASSERT_EQ(2, whichPowerOfTwo(4));
+			ASSERT_EQ(4, whichPowerOfTwo(16));
+			ASSERT_EQ(-1, whichPowerOfTwo(0));
+			ASSERT_EQ(-1, whichPowerOfTwo(-5));
+			ASSERT_EQ(-1, whichPowerOfTwo(7));
+		}
+		void arrrev(){
+			// regular
+			int srcArr[] = { 10, 20, 30 }; // odd number of entries
+			int destArr[] = { 30, 20, 10 };
+			int* pRev = new int[3];
+			yasi::arrrev(srcArr, 3, &pRev);
+			ASSERT_NE(0, (int)pRev) << "reversed array is NULL";
+			for (int i = 0; i < 3; i++){
+				ASSERT_EQ(destArr[i], pRev[i]) << "element mismatch at reverse index " << i;
+			}
+			DELETE_ARR_SAFE(pRev);
+
+			int srcArr2[] = { 10, 20, 30, 40 }; // even number of entries
+			int destArr2[] = { 40, 30, 20, 10 };
+			pRev = new int[4];
+			yasi::arrrev(srcArr2, 4, &pRev);
+			ASSERT_NE(0, (int)pRev) << "reversed array is NULL";
+			for (int i = 0; i < 4; i++){
+				ASSERT_EQ(destArr2[i], pRev[i]) << "element mismatch at reverse index " << i;
+			}
+			DELETE_ARR_SAFE(pRev);
+
+			// bad input
+			int* pNull = NULL;
+			yasi::arrrev(pNull, 3, &pRev);
+			ASSERT_EQ(0, (int)pRev) << "worked on a NULL pointer";
+			yasi::arrrev(srcArr, 0, &pRev);
+			ASSERT_EQ(0, (int)pRev) << "worked on zero size";
+			DELETE_ARR_SAFE(pRev);
+			yasi::arrrev(srcArr, -1, &pRev);
+			ASSERT_EQ(0, (int)pRev) << "worked on negativesize";
+			//DELETE_ARR_SAFE(pRev);
+		}
+		void strPurge(){
+			string str = "abedabecaebc";
+
+			// purge chars present
+			string str2 = yasi::strPurge(str, "de");
+			ASSERT_EQ("ababcabc", str2) << "failed";
+
+			// purge chars absent
+			str2 = yasi::strPurge(str, "x");
+			ASSERT_EQ(str, str2) << "failed";
+
+			// no chars given
+			str2 = yasi::strPurge(str, "");
+			ASSERT_EQ(str, str2) << "failed";
+		}
+	};
+
+	ADD_TEST_F(UtilsTest, arrrev);
+	ADD_TEST_F(UtilsTest, strPurge);
+	ADD_TEST_F(UtilsTest, whichPowerOfTwo_);
+
+#endif
+
+} // namespace yasi
\ No newline at end of file