diff --git a/Containers/public/AvlTree.hpp b/Containers/public/AvlTree.hpp
index 72a1ef5..bde6645 100644
--- a/Containers/public/AvlTree.hpp
+++ b/Containers/public/AvlTree.hpp
@@ -16,9 +16,9 @@ namespace tp {
     inline bool descentLeft(AvlNumericKey in) const { return in.val < val; }
     inline bool exactNode(AvlNumericKey in) const { return in.val == val; }
 
-    inline AvlNumericKey getFindKey(/**/) const { return val; }
-    inline AvlNumericKey keyInRightSubtree(AvlNumericKey in) const { return in.val; }
-    inline AvlNumericKey keyInLeftSubtree(AvlNumericKey in) const { return in.val; }
+    inline AvlNumericKey getFindKey(/**/) const { return *this; }
+    inline AvlNumericKey keyInRightSubtree(AvlNumericKey in) const { return in; }
+    inline AvlNumericKey keyInLeftSubtree(AvlNumericKey in) const { return in; }
 
     inline void updateTreeCacheCallBack() {}
 	};
@@ -47,7 +47,7 @@ namespace tp {
 
     private:
       inline bool descentRight(KeyArg aKey) const { return key.descentRight(aKey); }
-      inline bool descentLeft(KeyArg aKey) const { return key.descentRight(aKey); }
+      inline bool descentLeft(KeyArg aKey) const { return key.descentLeft(aKey); }
       inline bool exactNode(KeyArg aKey) const { return key.exactNode(aKey); }
 
       inline KeyArg getFindKey(const Node* node = nullptr) const { return key.getFindKey(/*node*/); }
@@ -73,7 +73,13 @@ namespace tp {
       return new (mAlloc.allocate(sizeof(Node))) Node(key, data);
     }
 
-		inline ualni getNodeHeight(const Node* node) const {
+    inline void injectNodeInstead(Node* place, Node* inject) {
+      // TODO : swap instead of copy
+      place->data = inject->data;
+      place->key = inject->key;
+    }
+
+		inline alni getNodeHeight(const Node* node) const {
 			return node ? node->mHeight : -1;
 		}
 
@@ -194,17 +200,18 @@ namespace tp {
 			if (head->exactNode(key)) {
 				if (head->mRight && head->mLeft) {
           Node* min = minNode(head->mRight);
-					head->data = min->data;
-					head->mRight = removeUtil(head->mRight, min->getFindKey(head->mRight));
+          auto const& newKey = min->getFindKey(head->mRight);
+          injectNodeInstead(head, min);
+					head->mRight = removeUtil(head->mRight, newKey);
 				}
 				else if (head->mRight) {
-					head->data = head->mRight->data;
+          injectNodeInstead(head, head->mRight);
 					deleteNode(head->mRight);
 					head->mRight = nullptr;
           mSize--;
 				}
 				else if (head->mLeft) {
-					head->data = head->mLeft->data;
+          injectNodeInstead(head, head->mLeft);
           deleteNode(head->mLeft);
 					head->mLeft = nullptr;
           mSize--;
@@ -337,13 +344,19 @@ namespace tp {
 				// TODO: incomplete test
 				if (!head->descentLeft(head->mLeft->getFindKey(head))) return head;
 				if (head->mLeft->mParent != head) return head;
+        if (!head->mRight && head->mLeft->mHeight != head->mHeight - 1) return head;
 			}
 
 			if (head->mRight) {
 				if (!head->descentRight(head->mRight->getFindKey(head))) return head;
 				if (head->mRight->mParent != head) return head;
+        if (!head->mLeft && head->mRight->mHeight != head->mHeight - 1) return head;
 			}
 
+      if (head->mLeft && head->mRight) {
+        if (max(head->mLeft->mHeight, head->mRight->mHeight) != head->mHeight - 1) return head;
+      }
+
 			int balance = getNodeHeight(head->mRight) - getNodeHeight(head->mLeft);
 
 			if (balance > 1 || balance < -1) return head;
diff --git a/Containers/tests/AvlTest.cpp b/Containers/tests/AvlTest.cpp
index 5c57729..1aada9d 100644
--- a/Containers/tests/AvlTest.cpp
+++ b/Containers/tests/AvlTest.cpp
@@ -26,6 +26,106 @@ TEST_DEF_STATIC(Simple) {
   TEST(tree.head() == nullptr);
 }
 
+TEST_DEF_STATIC(Persistance) {
+  AvlTree<AvlNumericKey<alni>, TestClass, TestAllocator> tree;
+
+  const auto size = 1000;
+
+  struct Item {
+    Item() : data(0) {}
+    bool presents = false;
+    TestClass data;
+  };
+
+  Item buff[size];
+
+  for (auto i : Range(size)) {
+    buff[i].data.setVal(i);
+  }
+
+  // random load
+  ualni loadSize = 0;
+  while (loadSize < size / 2) {
+    ualni idx = rand() % (size - 1);
+    DEBUG_ASSERT(idx < size)
+    if (!buff[idx].presents) {
+      tree.insert((alni) buff[idx].data.getVal(), buff[idx].data);
+      loadSize++;
+      buff[idx].presents = true;
+
+      TEST(tree.isValid());
+      TEST(tree.size() == loadSize);
+    }
+  }
+
+  for (auto& item : buff) {
+    if (item.presents) continue;
+    tree.insert((alni) item.data.getVal(), item.data);
+    loadSize++;
+    item.presents = true;
+
+    TEST(tree.isValid());
+    TEST(tree.size() == loadSize);
+  }
+
+  TEST(tree.size() == size);
+  TEST(tree.maxNode(tree.head())->data.getVal() == size - 1);
+  TEST(tree.minNode(tree.head())->data.getVal() == 0);
+
+  // find
+  for (auto item : buff) {
+    auto node = tree.find((alni) item.data.getVal());
+    TEST(node);
+    if (!node) continue;
+    TEST(node->data.getVal() == item.data.getVal());
+  }
+
+  TEST(!tree.find(size + 1));
+  TEST(!tree.find(-1));
+
+  // random unload
+  ualni unloadSize = 0;
+  while (unloadSize < size / 2) {
+    ualni idx = rand() % (size - 1);
+    if (buff[idx].presents) {
+
+      tree.remove((alni) buff[idx].data.getVal());
+
+      unloadSize++;
+      buff[idx].presents = false;
+
+      // find
+      for (auto item : buff) {
+        if (!item.presents) continue;
+        auto node = tree.find((alni) item.data.getVal());
+        TEST(node);
+        if (!node) continue;
+        TEST(node->data.getVal() == item.data.getVal());
+      }
+
+      TEST(tree.isValid());
+      TEST(tree.size() == size - unloadSize);
+    }
+  }
+
+  for (auto& item : buff) {
+    if (item.presents) {
+      tree.remove((alni) item.data.getVal());
+      unloadSize++;
+      item.presents = false;
+
+      TEST(tree.isValid());
+      TEST(tree.size() == size - unloadSize);
+    }
+  }
+
+  TEST(tree.size() == 0);
+  TEST(tree.head() == nullptr);
+  TEST(tree.maxNode(tree.head()) == nullptr);
+  TEST(tree.minNode(tree.head()) == nullptr);
+}
+
 TEST_DEF(Avl) {
   testSimple();
+  testPersistance();
 }
\ No newline at end of file
diff --git a/Module/tests/Tests.cpp b/Module/tests/Tests.cpp
index 3a04aa1..4e21c99 100644
--- a/Module/tests/Tests.cpp
+++ b/Module/tests/Tests.cpp
@@ -1,6 +1,8 @@
 
 #include "Module.hpp"
 
+#include "Common.hpp"
+
 int main() {
   tp::ModuleManifest* ModuleDependencies[] = { &tp::gModuleBase, nullptr };
   tp::ModuleManifest TestModule("Test", nullptr, nullptr, ModuleDependencies);
@@ -11,5 +13,10 @@ int main() {
 
   ASSERT(tp::gEnvironment.mWidth == tp::Environment::ArchWidth::X64);
 
+  ASSERT(tp::max(2, 1) == 2);
+  ASSERT(tp::max(-1, 0) == 0);
+  ASSERT(tp::max(0, -1) == 0);
+  ASSERT(tp::min(0, -1) == -1);
+
   TestModule.deinitialize();
 }
\ No newline at end of file