diff --git a/src/blobstore/implementations/onblocks/datatreestore/DataTree.cpp b/src/blobstore/implementations/onblocks/datatreestore/DataTree.cpp
index c8c43c05..058fea50 100644
--- a/src/blobstore/implementations/onblocks/datatreestore/DataTree.cpp
+++ b/src/blobstore/implementations/onblocks/datatreestore/DataTree.cpp
@@ -65,6 +65,9 @@ unique_ptr<DataLeafNode> DataTree::addDataLeafToFullTree() {
   return newLeaf;
 }
 
+const Key &DataTree::key() const {
+  return _rootNode->key();
+}
 
 
 }
diff --git a/src/blobstore/implementations/onblocks/datatreestore/DataTree.h b/src/blobstore/implementations/onblocks/datatreestore/DataTree.h
index 99cc653b..5f35121c 100644
--- a/src/blobstore/implementations/onblocks/datatreestore/DataTree.h
+++ b/src/blobstore/implementations/onblocks/datatreestore/DataTree.h
@@ -6,6 +6,9 @@
 #include "fspp/utils/macros.h"
 #include "impl/GetLowestRightBorderNodeWithLessThanKChildrenOrNull.h"
 
+namespace blockstore {
+class Key;
+}
 namespace blobstore {
 namespace onblocks {
 namespace datanodestore {
@@ -22,6 +25,8 @@ public:
   virtual ~DataTree();
 
   std::unique_ptr<datanodestore::DataLeafNode> addDataLeaf();
+
+  const blockstore::Key &key() const;
 private:
   datanodestore::DataNodeStore *_nodeStore;
   std::unique_ptr<datanodestore::DataNode> _rootNode;
diff --git a/src/test/blobstore/implementations/onblocks/datatreestore/DataTreeTest.cpp b/src/test/blobstore/implementations/onblocks/datatreestore/DataTreeTest.cpp
index b70194df..a7114d49 100644
--- a/src/test/blobstore/implementations/onblocks/datatreestore/DataTreeTest.cpp
+++ b/src/test/blobstore/implementations/onblocks/datatreestore/DataTreeTest.cpp
@@ -4,14 +4,22 @@
 #include "blobstore/implementations/onblocks/datanodestore/DataNodeStore.h"
 #include "blobstore/implementations/onblocks/datatreestore/DataTree.h"
 #include "blobstore/implementations/onblocks/datanodestore/DataLeafNode.h"
+#include "blobstore/implementations/onblocks/datanodestore/DataInnerNode.h"
+
+#include "fspp/utils/pointer.h"
 
 using ::testing::Test;
 using std::unique_ptr;
 using std::make_unique;
+using fspp::dynamic_pointer_move;
 
 using blobstore::onblocks::datanodestore::DataNodeStore;
 using blobstore::onblocks::datanodestore::DataNode;
+using blobstore::onblocks::datanodestore::DataInnerNode;
+using blobstore::onblocks::datanodestore::DataLeafNode;
 using blockstore::testfake::FakeBlockStore;
+using blockstore::BlockStore;
+using blockstore::Key;
 
 namespace blobstore {
 namespace onblocks {
@@ -28,9 +36,76 @@ public:
     return make_unique<DataTree>(&nodeStore, std::move(leafnode));
   }
 
+  Key CreateTreeAddOneLeafReturnRootKey() {
+    auto tree = CreateLeafOnlyTree();
+    auto key = tree->key();
+    tree->addDataLeaf();
+    return key;
+  }
+
+  Key CreateTreeAddTwoLeavesReturnRootKey() {
+    auto tree = CreateLeafOnlyTree();
+    auto key = tree->key();
+    tree->addDataLeaf();
+    tree->addDataLeaf();
+    return key;
+  }
+
+  unique_ptr<DataInnerNode> LoadInnerNode(const Key &key) {
+    auto node = nodeStore.load(key);
+    return dynamic_pointer_move<DataInnerNode>(node);
+  }
+
+  unique_ptr<DataLeafNode> LoadLeafNode(const Key &key) {
+    auto node = nodeStore.load(key);
+    return dynamic_pointer_move<DataLeafNode>(node);
+  }
+
+  void EXPECT_IS_LEAF_NODE(const Key &key) {
+    auto node = LoadLeafNode(key);
+    EXPECT_NE(nullptr, node.get());
+  }
+
+  void EXPECT_IS_INNER_NODE(const Key &key) {
+    auto node = LoadInnerNode(key);
+    EXPECT_NE(nullptr, node.get());
+  }
+
   DataNodeStore nodeStore;
 };
 
+TEST_F(DataTreeTest, GrowAOneNodeTree_KeyDoesntChange) {
+  auto tree = CreateLeafOnlyTree();
+  auto key = tree->key();
+  tree->addDataLeaf();
+  EXPECT_EQ(key, tree->key());
+}
+
+TEST_F(DataTreeTest, GrowAOneNodeTree_Structure) {
+  auto key = CreateTreeAddOneLeafReturnRootKey();
+
+  EXPECT_IS_INNER_NODE(key);
+  auto root = LoadInnerNode(key);
+
+  EXPECT_EQ(2u, root->numChildren());
+  EXPECT_IS_LEAF_NODE(root->getChild(0)->key());
+  EXPECT_IS_LEAF_NODE(root->getChild(1)->key());
+}
+
+TEST_F(DataTreeTest, GrowATwoNodeTree_Structure) {
+  auto key = CreateTreeAddTwoLeavesReturnRootKey();
+
+  EXPECT_IS_INNER_NODE(key);
+  auto root = LoadInnerNode(key);
+
+  EXPECT_EQ(3u, root->numChildren());
+  EXPECT_IS_LEAF_NODE(root->getChild(0)->key());
+  EXPECT_IS_LEAF_NODE(root->getChild(1)->key());
+  EXPECT_IS_LEAF_NODE(root->getChild(2)->key());
+}
+
+//TODO Test that when growing, the original leaf retains its data
+
 }
 }
 }