diff --git a/src/lol/algorithm/avl_tree.h b/src/lol/algorithm/avl_tree.h
index 8bf47848..e162d0f5 100644
--- a/src/lol/algorithm/avl_tree.h
+++ b/src/lol/algorithm/avl_tree.h
@@ -20,6 +20,8 @@ namespace lol
 template<typename K, typename V>
 class avl_tree
 {
+public:
+
     avl_tree() :
         m_root(0)
     {
@@ -35,9 +37,9 @@ class avl_tree
 
             if (created)
             {
-                this->m_root->path_update_balance(created);
+                this->m_root->path_update_balance(key);
 
-                tree_node * new_root = this->m_root->path_rebalance(created);
+                tree_node * new_root = this->m_root->path_rebalance(key);
                 if (new_root)
                     this->m_root = new_root;
             }
@@ -48,10 +50,12 @@ class avl_tree
         return true;
     }
 
-private:
+protected:
 
     class tree_node
     {
+    public:
+
         tree_node(K key, V value) :
             m_key(key),
             m_value(value),
@@ -100,7 +104,7 @@ private:
         {
             if (key < this->m_key)
             {
-                tree_node * node = this->m_lo->path_rebalance();
+                tree_node * node = this->m_lo->path_rebalance(key);
                 if (node)
                 {
                     this->m_lo = node;
@@ -109,7 +113,7 @@ private:
             }
             else if (this->m_key < key)
             {
-                tree_node * node = this->m_hi->path_rebalance();
+                tree_node * node = this->m_hi->path_rebalance(key);
                 if (node)
                 {
                     this->m_hi = node;
@@ -117,16 +121,16 @@ private:
                 }
             }
 
-            if (this->m_stairs_lo - this->m_stairs_hi == 2)
+            if (this->get_balance() == 2)
             {
-                return this->rotate();
+                return this->rotate(CW);
             }
-            else if (this->m_stairs_lo - this->m_stairs_hi == -2)
+            else if (this->get_balance() == -2)
             {
-                return this->rotate();
+                return this->rotate(CCW);
             }
             else
-                assert(lol::abs(this->m_stairs_lo - this->m_stairs_hi) < 3);
+                ASSERT(lol::abs(this->m_stairs_lo - this->m_stairs_hi) < 3);
         }
 
         enum Rotation { CW = 0, CCW = 1 };
@@ -169,7 +173,12 @@ private:
             this->m_stairs_hi = this->m_hi ? this->m_hi->m_stairs_lo + this->m_lo->m_stairs_hi : 0;
         }
 
-    private:
+        int get_balance()
+        {
+            return this->m_stairs_lo - this->m_stairs_hi;
+        }
+
+    protected:
 
         K m_key;
         V m_value;
diff --git a/src/t/algorithm/avl_tree.cpp b/src/t/algorithm/avl_tree.cpp
new file mode 100644
index 00000000..4c6ce83e
--- /dev/null
+++ b/src/t/algorithm/avl_tree.cpp
@@ -0,0 +1,66 @@
+//
+// Lol Engine
+//
+// Copyright: (c) 2010-2014 Sam Hocevar <sam@hocevar.net>
+//            (c) 2013-2014 Benjamin "Touky" Huet <huet.benjamin@gmail.com>
+//            (c) 2013-2014 Guillaume Bittoun <guillaume.bittoun@gmail.com>
+//   This program is free software; you can redistribute it and/or
+//   modify it under the terms of the Do What The Fuck You Want To
+//   Public License, Version 2, as published by Sam Hocevar. See
+//   http://www.wtfpl.net/ for more details.
+//
+
+#include <lol/engine-internal.h>
+
+#include <lolunit.h>
+
+namespace lol
+{
+
+class test_tree : public avl_tree<int, int>
+{
+public:
+
+	int get_root_balance()
+	{
+		return this->m_root->get_balance();
+	}
+};
+
+lolunit_declare_fixture(AvlTreeTest)
+{
+    void SetUp() {}
+
+    void TearDown() {}
+
+    lolunit_declare_test(AvlTreeInsert)
+    {
+        test_tree tree;
+
+        lolunit_assert_equal(tree.insert(1, 1), true);
+        lolunit_assert_equal(tree.insert(2, 3), true);
+        lolunit_assert_equal(tree.insert(2, 0), false);
+    }
+
+    lolunit_declare_test(AvlTreeBalanceCheck)
+    {
+        test_tree tree;
+
+        lolunit_assert_equal(tree.insert(1, 1), true);
+        lolunit_assert_equal(tree.get_root_balance(), 0);
+
+        lolunit_assert_equal(tree.insert(2, 1), true);
+        lolunit_assert_equal(tree.get_root_balance(), 1);
+
+        lolunit_assert_equal(tree.insert(3, 1), true);
+        lolunit_assert_equal(tree.get_root_balance(), 0);
+
+        lolunit_assert_equal(tree.insert(0, 1), true);
+        lolunit_assert_equal(tree.get_root_balance(), -1);
+
+        lolunit_assert_equal(tree.insert(-1, 1), true);
+        lolunit_assert_equal(tree.get_root_balance(), 0);
+    }
+};
+
+}