diff --git a/thu_dsa/chp5/binNode.h b/thu_dsa/chp5/binNode.h
index d6de521..9e02c22 100644
--- a/thu_dsa/chp5/binNode.h
+++ b/thu_dsa/chp5/binNode.h
@@ -68,7 +68,7 @@ void BinNode<T>::goAlongLeftBranch(Stack<BinNodePosi(T)> &S){
 template <typename T>
 int BinNode<T>::size() const {
 	int leftSize = this->leftChild ? this->leftChild->size() : 0;
-	int rightSize = this - rightChild ? this->rightChild->size() : 0;
+	int rightSize = this -> rightChild ? this->rightChild->size() : 0;
 	return leftSize + rightSize + 1;
 }
 
diff --git a/thu_dsa/chp5/testBinTree.cpp b/thu_dsa/chp5/testBinTree.cpp
index b01544a..3d50704 100644
--- a/thu_dsa/chp5/testBinTree.cpp
+++ b/thu_dsa/chp5/testBinTree.cpp
@@ -6,6 +6,7 @@ using std::cout;
 using std::endl;
 
 void test_insert();
+void test_size();
 void test_preTraversal();
 void test_inTraversal();
 void test_postTraversal();
@@ -15,6 +16,7 @@ int main(){
 	cout << "Running test." << endl;
 
 	test_insert();
+	test_size();
 	test_preTraversal();
 	test_inTraversal();
 	test_postTraversal();
@@ -56,6 +58,16 @@ void test_insert(){
 	assert(left->height == 0 && right->height == 0);
 }
 
+void test_size(){
+	BinTree<int> intTree;
+	BinNodePosi(int) root = intTree.insertAsRoot(8);
+	assert(root->size() == 1);
+	intTree.insertAsLC(root, 7);
+	assert(root->size() == 2);
+	intTree.insertAsRC(root, 14);
+	assert(root->size() == 3);
+}
+
 template <typename T>
 struct Print{
 	virtual void operator()(T const &val){