diff --git a/README.md b/README.md
index 70183898..aa2a491b 100644
--- a/README.md
+++ b/README.md
@@ -20,7 +20,9 @@
 
 **News**  
 
-- ⚠️ Attention! Oat++ main repo is bumping it's version to 1.4.0. While 1.4.0 is **IN DEVELOPMENT** use `1.3.0-latest` tag.
+- ⚠️ Attention! Oat++ main repo is bumping its version to 1.4.0. While 1.4.0 is **IN DEVELOPMENT** use `1.3.0-latest` tag.
+- Follow the [changelog](https://github.com/oatpp/oatpp/blob/master/changelog/1.4.0.md) for news and features in version `1.4.0`.
+- Consider supporting Oat++ via the [GitHub sponsors](https://github.com/sponsors/oatpp) page.
 
 ---
 
diff --git a/changelog/1.4.0.md b/changelog/1.4.0.md
index bfee515d..19bcd97d 100644
--- a/changelog/1.4.0.md
+++ b/changelog/1.4.0.md
@@ -8,6 +8,8 @@ Contents:
 
 - [URL Encoder And Decoder](#url-encoder-and-decoder)
 - [Introduce async::ConditionVariable](#async-condition-variable)
+- [oatpp::Tree](#oatpptree)
+- [Remapper](#remapper)
 - [Restructuring](#restructuring)
 
 
@@ -49,6 +51,61 @@ OATPP_ASSERT(decoded == data)
   ...
 ```
 
+## oatpp::Tree
+
+New mapping-enabled type `oatpp::Tree` for flexible data access.
+
+```cpp
+ENDPOINT("POST", "users", createUser,
+         BODY_DTO(oatpp::Tree, user))
+{
+  oatpp::String name = user["name"];
+  v_uint16 age = user["age"];
+  
+  auto& subs = user["subscriptions"].getVector();
+  for(auto& s : subs) {
+    ...
+  }
+  ...
+}
+```
+
+Any node of oatpp::Tree can be mapped to DTO or to any mapping-enabled oatpp type - see [Remapper](#remapper)
+
+## Remapper
+
+`oatpp::data::mapping::Remapper`.  
+
+Remapper can be user to remap any oatpp type to any oatpp type.
+UnorderedFields can be mapped to DTOs, DTOs to vectors of values, vector items to other DTOs, DTOs to Trees, etc...
+
+```cpp
+class User : public oatpp::DTO {
+  
+  DTO_INIT(User, DTO)
+  
+  DTO_FIELD(String, name);
+  DTO_FIELD(UInt32, age);
+  
+};
+
+...
+
+oatpp::data::mapping::Remapper remapper;
+
+auto user = User::createShared();
+user->name = "Jane";
+user->age = "25";
+
+auto tree = remapper.remap<oatpp::Tree>(user); // remap to tree
+auto fields = remapper.remap<oatpp::Fields<oatpp::Tree>>(user); // remap to Fields 
+auto otherDto = remapper.remap<oatpp::Object<OtherDto>>(user); // remap to OtherDto
+auto values = remapper.remap<oatpp::Vector<oatpp::Tree>>(user); // remap to Vector
+
+oatpp::String name = values[0];
+v_uint32 age = values[1];
+```
+
 ## Restructuring
 
 ### Files
diff --git a/src/oatpp/data/mapping/ObjectRemapper.cpp b/src/oatpp/data/mapping/ObjectRemapper.cpp
index ed301307..f9b43a5f 100644
--- a/src/oatpp/data/mapping/ObjectRemapper.cpp
+++ b/src/oatpp/data/mapping/ObjectRemapper.cpp
@@ -26,9 +26,9 @@
 
 namespace oatpp { namespace data { namespace mapping {
 
-oatpp::Void ObjectRemapper::mapTree(const Tree* tree, const oatpp::Type* toType, ErrorStack& errorStack) const {
+oatpp::Void ObjectRemapper::remap(const Tree& tree, const oatpp::Type* toType, ErrorStack& errorStack) const {
   TreeToObjectMapper::State state;
-  state.tree = tree;
+  state.tree = std::addressof(tree);
   state.config = &m_treeToObjectConfig;
   const auto & result = m_treeToObjectMapper.map(state, toType);
   if(!state.errorStack.empty()) {
@@ -40,10 +40,14 @@ oatpp::Void ObjectRemapper::mapTree(const Tree* tree, const oatpp::Type* toType,
 
 oatpp::Void ObjectRemapper::remap(const oatpp::Void& polymorph, const oatpp::Type* toType, ErrorStack& errorStack) const {
 
+  if(polymorph == nullptr) {
+    return nullptr;
+  }
+
   /* if polymorph is a Tree - we can map it right away */
   if(polymorph.getValueType() == oatpp::Tree::Class::getType()) {
     auto tree = static_cast<const Tree*>(polymorph.get());
-    return mapTree(tree, toType, errorStack);
+    return remap(*tree, toType, errorStack);
   }
 
   Tree tree;
@@ -64,7 +68,7 @@ oatpp::Void ObjectRemapper::remap(const oatpp::Void& polymorph, const oatpp::Typ
     return oatpp::Tree(std::move(tree));
   }
 
-  return mapTree(&tree, toType, errorStack);
+  return remap(tree, toType, errorStack);
 
 }
 
diff --git a/src/oatpp/data/mapping/ObjectRemapper.hpp b/src/oatpp/data/mapping/ObjectRemapper.hpp
index 979c0a47..674a0804 100644
--- a/src/oatpp/data/mapping/ObjectRemapper.hpp
+++ b/src/oatpp/data/mapping/ObjectRemapper.hpp
@@ -33,8 +33,6 @@
 namespace oatpp { namespace data { namespace mapping {
 
 class ObjectRemapper {
-protected:
-  oatpp::Void mapTree(const Tree* tree, const oatpp::Type* toType, ErrorStack& errorStack) const;
 protected:
   ObjectToTreeMapper::Config m_objectToTreeConfig;
   TreeToObjectMapper::Config m_treeToObjectConfig;
@@ -45,6 +43,25 @@ public:
   ObjectRemapper() = default;
   virtual ~ObjectRemapper() = default;
 
+  oatpp::Void remap(const Tree& tree, const oatpp::Type* toType, ErrorStack& errorStack) const;
+
+  template<class Wrapper>
+  Wrapper remap(const Tree& tree, ErrorStack& errorStack) const {
+    auto toType = Wrapper::Class::getType();
+    return remap(tree, toType, errorStack).template cast<Wrapper>();
+  }
+
+  template<class Wrapper>
+  Wrapper remap(const Tree& tree) const {
+    auto toType = Wrapper::Class::getType();
+    ErrorStack errorStack;
+    const auto& result = remap(tree, toType, errorStack).template cast<Wrapper>();
+    if(!errorStack.empty()) {
+      throw MappingError(std::move(errorStack));
+    }
+    return result;
+  }
+
   oatpp::Void remap(const oatpp::Void& polymorph, const oatpp::Type* toType, ErrorStack& errorStack) const;
 
   template<class Wrapper>
diff --git a/src/oatpp/data/mapping/Tree.cpp b/src/oatpp/data/mapping/Tree.cpp
index ef6db988..3d52bffb 100644
--- a/src/oatpp/data/mapping/Tree.cpp
+++ b/src/oatpp/data/mapping/Tree.cpp
@@ -36,8 +36,10 @@ Tree::Attributes::Attributes()
 {}
 
 Tree::Attributes::Attributes(const Attributes& other)
-  : m_attributes(other.m_attributes != nullptr ? new std::unordered_map<type::String, type::String>(*other.m_attributes) : nullptr)
-{}
+  : Attributes()
+{
+  operator=(other);
+}
 
 Tree::Attributes::Attributes(Attributes&& other) noexcept
   : m_attributes(other.m_attributes)
@@ -46,37 +48,101 @@ Tree::Attributes::Attributes(Attributes&& other) noexcept
 }
 
 Tree::Attributes& Tree::Attributes::operator = (const Attributes& other) {
+
   if(other.m_attributes) {
+
     if(m_attributes) {
       *m_attributes = *other.m_attributes;
     } else {
-      m_attributes = new std::unordered_map<type::String, type::String>(*other.m_attributes);
+      m_attributes = new Attrs(*other.m_attributes);
     }
+
+    for(auto & po : m_attributes->order){
+      po.second = &m_attributes->map.at(po.first.lock());
+    }
+
   } else {
     delete m_attributes;
     m_attributes = nullptr;
   }
+
   return *this;
 }
 
 Tree::Attributes& Tree::Attributes::operator = (Attributes&& other) noexcept {
+
   delete m_attributes;
+
   m_attributes = other.m_attributes;
   other.m_attributes = nullptr;
+
   return *this;
 }
 
 Tree::Attributes::~Attributes() {
   delete m_attributes;
+  m_attributes = nullptr;
+}
+
+void Tree::Attributes::initAttributes() {
+  if(m_attributes == nullptr)  {
+    m_attributes = new Attrs();
+  }
+}
+
+type::String& Tree::Attributes::operator [] (const type::String& key) {
+  initAttributes();
+  auto it = m_attributes->map.find(key);
+  if(it == m_attributes->map.end()) {
+    auto& result = m_attributes->map[key];
+    m_attributes->order.emplace_back(key.getPtr(), &result);
+    return result;
+  }
+  return it->second;
+}
+
+const type::String& Tree::Attributes::operator [] (const type::String& key) const {
+  if(m_attributes != nullptr) {
+    auto it = m_attributes->map.find(key);
+    if (it != m_attributes->map.end()) {
+      return it->second;
+    }
+  }
+  throw std::runtime_error("[oatpp::data::mapping::Tree::Attributes::operator []]: const operator[] can't add items.");
+}
+
+std::pair<type::String, std::reference_wrapper<type::String>> Tree::Attributes::operator [] (v_uint64 index) {
+  if(m_attributes != nullptr) {
+    auto &item = m_attributes->order.at(index);
+    return {item.first.lock(), *item.second};
+  }
+  throw std::runtime_error("[oatpp::data::mapping::Tree::Attributes::operator []]: const operator[] can't get item - empty attributes.");
+}
+
+std::pair<type::String, std::reference_wrapper<const type::String>> Tree::Attributes::operator [] (v_uint64 index) const {
+  if(m_attributes != nullptr) {
+    auto &item = m_attributes->order.at(index);
+    return {item.first.lock(), *item.second};
+  }
+  throw std::runtime_error("[oatpp::data::mapping::Tree::Attributes::operator []]: const operator[] can't get item - empty attributes.");
+}
+
+type::String Tree::Attributes::get(const type::String& key) const {
+  if(m_attributes == nullptr) return nullptr;
+  auto it = m_attributes->map.find(key);
+  if(it != m_attributes->map.end()) {
+    return it->second;
+  }
+  return nullptr;
 }
 
 bool Tree::Attributes::empty() const {
-  return m_attributes == nullptr || m_attributes->empty();
+  return m_attributes == nullptr || m_attributes->map.empty();
 }
 
 v_uint64 Tree::Attributes::size() const {
   if(m_attributes) {
-    return m_attributes->size();
+    return m_attributes->map.size();
   }
   return 0;
 }
@@ -725,13 +791,9 @@ TreeMap::TreeMap(TreeMap&& other) noexcept {
 
 TreeMap& TreeMap::operator = (const TreeMap& other) {
   m_map = other.m_map;
-  m_order.resize(other.m_order.size());
-  for(v_uint64 i = 0; i < other.m_order.size(); i ++) {
-    auto& po = other.m_order[i];
-    auto& pt = m_order[i];
-    pt.first = po.first;
-
-    pt.second = &m_map.at(po.first.lock());
+  m_order = other.m_order;
+  for(auto & po : m_order){
+    po.second = &m_map.at(po.first.lock());
   }
   return *this;
 }
diff --git a/src/oatpp/data/mapping/Tree.hpp b/src/oatpp/data/mapping/Tree.hpp
index 7817a3a6..5b8f2383 100644
--- a/src/oatpp/data/mapping/Tree.hpp
+++ b/src/oatpp/data/mapping/Tree.hpp
@@ -72,7 +72,14 @@ public:
 
   class Attributes {
   private:
-    std::unordered_map<type::String, type::String>* m_attributes;
+    struct Attrs {
+      std::unordered_map<type::String, type::String> map;
+      std::vector<std::pair<std::weak_ptr<std::string>, type::String*>> order;
+    };
+  private:
+    void initAttributes();
+  private:
+    Attrs* m_attributes;
   public:
 
     Attributes();
@@ -84,8 +91,15 @@ public:
 
     ~Attributes();
 
-    bool empty() const;
+    type::String& operator [] (const type::String& key);
+    const type::String& operator [] (const type::String& key) const;
 
+    std::pair<type::String, std::reference_wrapper<type::String>> operator [] (v_uint64 index);
+    std::pair<type::String, std::reference_wrapper<const type::String>> operator [] (v_uint64 index) const;
+
+    type::String get(const type::String& key) const;
+
+    bool empty() const;
     v_uint64 size() const;
 
   };
diff --git a/src/oatpp/data/type/Object.hpp b/src/oatpp/data/type/Object.hpp
index 204e0d33..bd0634ae 100644
--- a/src/oatpp/data/type/Object.hpp
+++ b/src/oatpp/data/type/Object.hpp
@@ -435,6 +435,7 @@ private:
 public:
   typedef oatpp::data::type::Void Void;
   typedef oatpp::data::type::Any Any;
+  typedef oatpp::data::type::Tree Tree;
   typedef oatpp::data::type::String String;
   typedef oatpp::data::type::Int8 Int8;
   typedef oatpp::data::type::UInt8 UInt8;
diff --git a/src/oatpp/data/type/Tree.cpp b/src/oatpp/data/type/Tree.cpp
index 7a69c9de..91fc3661 100644
--- a/src/oatpp/data/type/Tree.cpp
+++ b/src/oatpp/data/type/Tree.cpp
@@ -123,6 +123,27 @@ bool Tree::operator != (const Tree& other) const {
   return !operator == (other);
 }
 
+mapping::Tree* Tree::operator->() {
+  if(!m_ptr) {
+    m_ptr = std::make_shared<mapping::Tree>();
+  }
+  return m_ptr.get();
+}
+
+mapping::Tree* Tree::operator->() const {
+  if(!m_ptr) {
+    throw std::runtime_error("[oatpp::data::type::Tree::operator ->()]: null-pointer exception");
+  }
+  return m_ptr.get();
+}
+
+mapping::Tree& Tree::operator*() {
+  if(!m_ptr) {
+    m_ptr = std::make_shared<mapping::Tree>();
+  }
+  return *m_ptr;
+}
+
 const mapping::Tree& Tree::operator*() const {
   if(!m_ptr) {
     throw std::runtime_error("[oatpp::data::type::Tree::operator *()]: null-pointer exception");
@@ -130,12 +151,32 @@ const mapping::Tree& Tree::operator*() const {
   return *m_ptr;
 }
 
-mapping::Tree& Tree::operator*() {
+mapping::Tree& Tree::operator [] (const String& key) {
   if(!m_ptr) {
-    throw std::runtime_error("[oatpp::data::type::Tree::operator *()]: null-pointer exception");
+    m_ptr = std::make_shared<mapping::Tree>();
   }
-  return *m_ptr;
+  return (*m_ptr)[key];
 }
 
+const mapping::Tree& Tree::operator [] (const String& key) const {
+  if(!m_ptr) {
+    throw std::runtime_error("[oatpp::data::type::Tree::operator []]: null-pointer exception");
+  }
+  return (*m_ptr)[key];
+}
+
+mapping::Tree& Tree::operator [] (v_uint64 index) {
+  if(!m_ptr) {
+    m_ptr = std::make_shared<mapping::Tree>();
+  }
+  return (*m_ptr)[index];
+}
+
+const mapping::Tree& Tree::operator [] (v_uint64 index) const {
+  if(!m_ptr) {
+    throw std::runtime_error("[oatpp::data::type::Tree::operator []]: null-pointer exception");
+  }
+  return (*m_ptr)[index];
+}
 
 }}}
diff --git a/src/oatpp/data/type/Tree.hpp b/src/oatpp/data/type/Tree.hpp
index b59f4f4a..8aebb596 100644
--- a/src/oatpp/data/type/Tree.hpp
+++ b/src/oatpp/data/type/Tree.hpp
@@ -26,6 +26,7 @@
 #define oatpp_data_type_Tree_hpp
 
 #include "./Type.hpp"
+#include "./Primitive.hpp"
 
 namespace oatpp { namespace data { namespace mapping {
 
@@ -108,8 +109,17 @@ public:
   bool operator == (const Tree& other) const;
   bool operator != (const Tree& other) const;
 
-  const mapping::Tree& operator*() const;
+  mapping::Tree* operator->();
+  mapping::Tree* operator->() const;
+
   mapping::Tree& operator*();
+  const mapping::Tree& operator*() const;
+
+  mapping::Tree& operator [] (const String& key);
+  const mapping::Tree& operator [] (const String& key) const;
+
+  mapping::Tree& operator [] (v_uint64 index);
+  const mapping::Tree& operator [] (v_uint64 index) const;
 
 };
 
diff --git a/test/oatpp/AllTestsMain.cpp b/test/oatpp/AllTestsMain.cpp
index 64ac350c..7720e06e 100644
--- a/test/oatpp/AllTestsMain.cpp
+++ b/test/oatpp/AllTestsMain.cpp
@@ -247,8 +247,6 @@ void runTests() {
 
   }
 
-
-
 }
 
 }
diff --git a/test/oatpp/data/mapping/ObjectRemapperTest.cpp b/test/oatpp/data/mapping/ObjectRemapperTest.cpp
index 863bc5b0..dd8c3000 100644
--- a/test/oatpp/data/mapping/ObjectRemapperTest.cpp
+++ b/test/oatpp/data/mapping/ObjectRemapperTest.cpp
@@ -168,6 +168,57 @@ void ObjectRemapperTest::onRun() {
     OATPP_ASSERT(vec[4] == nullptr)
   }
 
+  {
+
+    OATPP_LOGD(TAG, "Remap tree fragments")
+
+    Tree tree;
+    tree.setVector(3);
+
+    tree[0]["field_1"] = "val1";
+    tree[0]["field_2"] = "val2";
+
+    tree[1]["field_1"] = "val1.2";
+    tree[1]["field_2"] = "val2.2";
+
+    tree[2]["field_1"] = "val1.3";
+    tree[2]["field_2"] = "val2.3";
+
+    {
+      auto map = remapper.remap<oatpp::UnorderedFields<String>>(tree[0]);
+      OATPP_ASSERT(map->size() == 2)
+      OATPP_ASSERT(map["field_1"] == "val1")
+      OATPP_ASSERT(map["field_2"] == "val2")
+    }
+
+    {
+      auto map = remapper.remap<oatpp::UnorderedFields<String>>(tree[1]);
+      OATPP_ASSERT(map->size() == 2)
+      OATPP_ASSERT(map["field_1"] == "val1.2")
+      OATPP_ASSERT(map["field_2"] == "val2.2")
+    }
+
+    {
+      auto map = remapper.remap<oatpp::UnorderedFields<String>>(tree[2]);
+      OATPP_ASSERT(map->size() == 2)
+      OATPP_ASSERT(map["field_1"] == "val1.3")
+      OATPP_ASSERT(map["field_2"] == "val2.3")
+    }
+
+  }
+
+  {
+    oatpp::Tree tree;
+    OATPP_ASSERT(tree == nullptr)
+
+    OATPP_ASSERT(tree->isUndefined()) // implicitly initialized
+    OATPP_ASSERT(tree != nullptr)
+
+    tree["hello"] = "world";
+    std::cout << *tree->debugPrint() << std::endl;
+
+  }
+
 }
 
 }}}
diff --git a/test/oatpp/data/mapping/TreeTest.cpp b/test/oatpp/data/mapping/TreeTest.cpp
index ef7721a8..62a44f35 100644
--- a/test/oatpp/data/mapping/TreeTest.cpp
+++ b/test/oatpp/data/mapping/TreeTest.cpp
@@ -36,6 +36,8 @@ namespace {
 template<typename T>
 void testTreeValue(T value) {
 
+  OATPP_LOGD("TEST", "Test value retrieval for '%s'", Tree::NodePrimitiveType<T>::name)
+
   Tree node;
 
   //node.setValue<T>(value);
@@ -70,6 +72,7 @@ void TreeTest::onRun() {
   testTreeValue<v_float64>(16);
 
   {
+    OATPP_LOGD(TAG, "Case 1")
     Tree node;
     oatpp::String original = "Hello World!";
     node.setString(original);
@@ -79,6 +82,7 @@ void TreeTest::onRun() {
   }
 
   {
+    OATPP_LOGD(TAG, "Case 2")
     Tree node1;
     Tree node2;
 
@@ -93,6 +97,7 @@ void TreeTest::onRun() {
   }
 
   {
+    OATPP_LOGD(TAG, "Case 3")
     Tree node1;
     Tree node2;
 
@@ -105,6 +110,7 @@ void TreeTest::onRun() {
   }
 
   {
+    OATPP_LOGD(TAG, "Case 4")
     std::vector<Tree> originalVector(10);
     for(v_uint32 i = 0; i < 10; i ++) {
       originalVector.at(i).setValue(i);
@@ -132,6 +138,7 @@ void TreeTest::onRun() {
   }
 
   {
+    OATPP_LOGD(TAG, "Case 5")
     TreeMap originalMap;
     for(v_uint32 i = 0; i < 10; i ++) {
       originalMap["node_" + utils::Conversion::int32ToStr(static_cast<v_int32>(i))].setValue(i);
@@ -156,6 +163,7 @@ void TreeTest::onRun() {
   }
 
   {
+    OATPP_LOGD(TAG, "Case 6")
     Tree article;
     oatpp::Tree ot;
 
@@ -176,6 +184,120 @@ void TreeTest::onRun() {
 
   }
 
+  {
+
+    OATPP_LOGD(TAG, "Attributes Case 1")
+    OATPP_LOGD(TAG, "size of Tree::Attributes='%lu'", sizeof(Tree::Attributes))
+
+    Tree::Attributes attr;
+
+    attr["key1"] = "value1";
+    attr["key1"] = "value1.2";
+    attr["key2"] = "value2";
+
+    OATPP_ASSERT(attr.size() == 2)
+
+    OATPP_ASSERT(attr["key1"] == "value1.2")
+    OATPP_ASSERT(attr["key2"] == "value2")
+    OATPP_ASSERT(attr["key3"] == nullptr) // key3 added
+
+    OATPP_ASSERT(attr.size() == 3)
+
+    OATPP_ASSERT(attr[0].second.get() == "value1.2")
+    OATPP_ASSERT(attr[1].second.get() == "value2")
+    OATPP_ASSERT(attr[2].second.get() == nullptr)
+
+  }
+
+  {
+
+    OATPP_LOGD(TAG, "Attributes Case 2")
+
+    Tree::Attributes attr1;
+    Tree::Attributes attr2;
+
+    attr1["key1"] = "value1";
+    attr1["key2"] = "value2";
+    attr1["key3"] = nullptr;
+
+    attr2["key1"] = "v1";
+    attr2["key2"] = "v2";
+
+    attr2 = attr1;
+
+    attr1["key1"] = "1";
+    attr1["key2"] = "2";
+    attr1["key3"] = "3";
+
+    OATPP_ASSERT(attr1[0].second.get() == "1")
+    OATPP_ASSERT(attr1[1].second.get() == "2")
+    OATPP_ASSERT(attr1[2].second.get() == "3")
+
+    OATPP_ASSERT(attr1["key1"] == "1")
+    OATPP_ASSERT(attr1["key2"] == "2")
+    OATPP_ASSERT(attr1["key3"] == "3")
+
+    OATPP_ASSERT(attr2[0].second.get() == "value1")
+    OATPP_ASSERT(attr2[1].second.get() == "value2")
+    OATPP_ASSERT(attr2[2].second.get() == nullptr)
+
+    OATPP_ASSERT(attr2["key1"] == "value1")
+    OATPP_ASSERT(attr2["key2"] == "value2")
+    OATPP_ASSERT(attr2["key3"] == nullptr)
+
+    Tree::Attributes attr3;
+    attr2 = attr3;
+
+    OATPP_ASSERT(attr2.empty())
+
+  }
+
+  {
+
+    OATPP_LOGD(TAG, "Attributes Case 3")
+
+    Tree tree1;
+    Tree tree2;
+
+    tree1 = "hello";
+    tree2 = "world";
+
+    tree1.attributes()["key1"] = "value1";
+    tree1.attributes()["key2"] = "value2";
+    tree1.attributes()["key3"] = nullptr;
+
+    tree2.attributes()["key1"] = "v1";
+    tree2.attributes()["key2"] = "v2";
+
+    tree2 = tree1;
+
+    tree1.attributes()["key1"] = "1";
+    tree1.attributes()["key2"] = "2";
+    tree1.attributes()["key3"] = "3";
+
+    OATPP_ASSERT(tree1.attributes()[0].second.get() == "1")
+    OATPP_ASSERT(tree1.attributes()[1].second.get() == "2")
+    OATPP_ASSERT(tree1.attributes()[2].second.get() == "3")
+
+    OATPP_ASSERT(tree1.attributes()["key1"] == "1")
+    OATPP_ASSERT(tree1.attributes()["key2"] == "2")
+    OATPP_ASSERT(tree1.attributes()["key3"] == "3")
+
+    OATPP_ASSERT(tree2.attributes()[0].second.get() == "value1")
+    OATPP_ASSERT(tree2.attributes()[1].second.get() == "value2")
+    OATPP_ASSERT(tree2.attributes()[2].second.get() == nullptr)
+
+    OATPP_ASSERT(tree2.attributes()["key1"] == "value1")
+    OATPP_ASSERT(tree2.attributes()["key2"] == "value2")
+    OATPP_ASSERT(tree2.attributes()["key3"] == nullptr)
+
+    Tree tree3;
+    tree2 = tree3;
+
+    OATPP_ASSERT(tree2.attributes().empty())
+
+  }
+
 }
 
 }}}