diff --git a/src/blobstore/implementations/onblocks/datanodestore/DataInnerNode.cpp b/src/blobstore/implementations/onblocks/datanodestore/DataInnerNode.cpp
index 5f42105f..d562bdc8 100644
--- a/src/blobstore/implementations/onblocks/datanodestore/DataInnerNode.cpp
+++ b/src/blobstore/implementations/onblocks/datanodestore/DataInnerNode.cpp
@@ -21,7 +21,7 @@ DataInnerNode::~DataInnerNode() {
 void DataInnerNode::InitializeNewNode(const DataNode &first_child) {
   *node().Depth() = first_child.depth() + 1;
   *node().Size() = 1;
-  first_child.key().ToBinary(ChildrenBegin()->key);
+  ChildrenBegin()->setKey(first_child.key());
 }
 
 uint32_t DataInnerNode::numChildren() const {
@@ -44,10 +44,30 @@ const DataInnerNode::ChildEntry *DataInnerNode::ChildrenEnd() const {
   return ChildrenBegin() + *node().Size();
 }
 
-const DataInnerNode::ChildEntry *DataInnerNode::RightmostExistingChild() const{
+DataInnerNode::ChildEntry *DataInnerNode::LastChild() {
+  return const_cast<ChildEntry*>(const_cast<const DataInnerNode*>(this)->LastChild());
+}
+
+const DataInnerNode::ChildEntry *DataInnerNode::LastChild() const {
   return ChildrenEnd()-1;
 }
 
+DataInnerNode::ChildEntry *DataInnerNode::getChild(unsigned int index) {
+  return const_cast<ChildEntry*>(const_cast<const DataInnerNode*>(this)->getChild(index));
+}
+
+const DataInnerNode::ChildEntry *DataInnerNode::getChild(unsigned int index) const {
+  assert(index < numChildren());
+  return ChildrenBegin()+index;
+}
+
+void DataInnerNode::addChild(const DataNode &child) {
+  assert(numChildren() < DataInnerNode::MAX_STORED_CHILDREN);
+  assert(child.depth() == depth()-1);
+  *node().Size() += 1;
+  LastChild()->setKey(child.key());
+}
+
 }
 }
 }
diff --git a/src/blobstore/implementations/onblocks/datanodestore/DataInnerNode.h b/src/blobstore/implementations/onblocks/datanodestore/DataInnerNode.h
index 9ba07c88..fecc9229 100644
--- a/src/blobstore/implementations/onblocks/datanodestore/DataInnerNode.h
+++ b/src/blobstore/implementations/onblocks/datanodestore/DataInnerNode.h
@@ -14,21 +14,37 @@ public:
   virtual ~DataInnerNode();
 
   struct ChildEntry {
-    uint8_t key[blockstore::Key::KEYLENGTH_BINARY];
+  public:
+    blockstore::Key key() const {
+      return blockstore::Key::FromBinary(_keydata);
+    }
+  private:
+    void setKey(const blockstore::Key &key) {
+      key.ToBinary(_keydata);
+    }
+    friend class DataInnerNode;
+    uint8_t _keydata[blockstore::Key::KEYLENGTH_BINARY];
+    DISALLOW_COPY_AND_ASSIGN(ChildEntry);
   };
 
   static constexpr uint32_t MAX_STORED_CHILDREN = DataNodeView::DATASIZE_BYTES / sizeof(ChildEntry);
 
-  void InitializeNewNode(const DataNode &first_child);
+  void InitializeNewNode(const DataNode &first_child_key);
 
   ChildEntry *ChildrenBegin();
   ChildEntry *ChildrenEnd();
   const ChildEntry *ChildrenBegin() const;
   const ChildEntry *ChildrenEnd() const;
 
-  const ChildEntry *RightmostExistingChild() const;
+  ChildEntry *getChild(unsigned int index);
+  const ChildEntry *getChild(unsigned int index) const;
+
+  ChildEntry *LastChild();
+  const ChildEntry *LastChild() const;
 
   uint32_t numChildren() const;
+
+  void addChild(const DataNode &child_key);
 };
 
 }
diff --git a/src/test/blobstore/implementations/onblocks/datanodestore/DataInnerNodeTest.cpp b/src/test/blobstore/implementations/onblocks/datanodestore/DataInnerNodeTest.cpp
index 8ad1dfb5..69b087f0 100644
--- a/src/test/blobstore/implementations/onblocks/datanodestore/DataInnerNodeTest.cpp
+++ b/src/test/blobstore/implementations/onblocks/datanodestore/DataInnerNodeTest.cpp
@@ -1 +1,64 @@
-//TODO
+#include <gtest/gtest.h>
+
+#include <blobstore/implementations/onblocks/datanodestore/DataInnerNode.h>
+#include <blobstore/implementations/onblocks/datanodestore/DataLeafNode.h>
+#include <blobstore/implementations/onblocks/datanodestore/DataNodeStore.h>
+
+#include "blockstore/implementations/testfake/FakeBlockStore.h"
+#include "blockstore/implementations/testfake/FakeBlock.h"
+
+#include <memory>
+
+using ::testing::Test;
+
+using blockstore::Key;
+using blockstore::testfake::FakeBlockStore;
+using blockstore::BlockStore;
+using namespace blobstore;
+using namespace blobstore::onblocks;
+using namespace blobstore::onblocks::datanodestore;
+
+using std::unique_ptr;
+using std::make_unique;
+
+class DataInnerNodeTest: public Test {
+public:
+  DataInnerNodeTest() :
+    _blockStore(make_unique<FakeBlockStore>()),
+    blockStore(_blockStore.get()),
+    nodeStore(make_unique<DataNodeStore>(std::move(_blockStore))),
+    leaf(nodeStore->createNewLeafNode()),
+    node(nodeStore->createNewInnerNode(*leaf)) {
+  }
+
+  unique_ptr<BlockStore> _blockStore;
+  BlockStore *blockStore;
+  unique_ptr<DataNodeStore> nodeStore;
+  unique_ptr<DataLeafNode> leaf;
+  unique_ptr<DataInnerNode> node;
+};
+
+TEST_F(DataInnerNodeTest, InitializesCorrectly) {
+  node->InitializeNewNode(*leaf);
+  EXPECT_EQ(1u, node->numChildren());
+  EXPECT_EQ(leaf->key(), node->getChild(0)->key());
+}
+
+TEST_F(DataInnerNodeTest, ReinitializesCorrectly) {
+  node->InitializeNewNode(*leaf);
+  auto leaf2 = nodeStore->createNewLeafNode();
+  node->addChild(*leaf2);
+  node->InitializeNewNode(*leaf);
+
+  EXPECT_EQ(1u, node->numChildren());
+  EXPECT_EQ(leaf->key(), node->getChild(0)->key());
+}
+
+TEST_F(DataInnerNodeTest, AddingASecondLeaf) {
+  auto leaf2 = nodeStore->createNewLeafNode();
+  node->addChild(*leaf2);
+
+  EXPECT_EQ(2u, node->numChildren());
+  EXPECT_EQ(leaf->key(), node->getChild(0)->key());
+  EXPECT_EQ(leaf2->key(), node->getChild(1)->key());
+}
diff --git a/src/test/blobstore/implementations/onblocks/datanodestore/DataNodeStoreTest.cpp b/src/test/blobstore/implementations/onblocks/datanodestore/DataNodeStoreTest.cpp
index 68a9938d..de3dd4b1 100644
--- a/src/test/blobstore/implementations/onblocks/datanodestore/DataNodeStoreTest.cpp
+++ b/src/test/blobstore/implementations/onblocks/datanodestore/DataNodeStoreTest.cpp
@@ -80,3 +80,15 @@ TEST_F(DataNodeStoreTest, DataNodeCrashesOnLoadIfDepthIsTooHigh) {
     nodeStore->load(key)
   );
 }
+
+TEST_F(DataNodeStoreTest, CreatedInnerNodeIsInitialized) {
+  auto leaf = nodeStore->createNewLeafNode();
+  auto node = nodeStore->createNewInnerNode(*leaf);
+  EXPECT_EQ(1u, node->numChildren());
+  EXPECT_EQ(leaf->key(), node->getChild(0)->key());
+}
+
+TEST_F(DataNodeStoreTest, CreatedLeafNodeIsInitialized) {
+  auto leaf = nodeStore->createNewLeafNode();
+  EXPECT_EQ(0u, leaf->numBytes());
+}