diff --git a/.archive/bplustree.go b/bplustree.go
similarity index 99%
rename from .archive/bplustree.go
rename to bplustree.go
index 79a257a..7fdab1b 100644
--- a/.archive/bplustree.go
+++ b/bplustree.go
@@ -100,14 +100,14 @@ func (tree *BPlusTree) Insert(key int, value interface{}) {
 	index := sort.SearchInts(leaf.keys, key)
 	leaf.keys = append(leaf.keys[:index], append([]int{key}, leaf.keys[index:]...)...)
 
+	if len(leaf.keys) > int(tree.maxKeys) {
+		tree.splitNode(leaf)
+	}
+
 	if len(tree.root.keys) > int(tree.maxKeys) {
 		tree.SplitRoot()
 		return
 	}
-
-	if len(leaf.keys) > int(tree.maxKeys) {
-		tree.splitNode(leaf)
-	}
 }
 
 func (tree *BPlusTree) findLeaf(key int) *BPlusTreeNode {
@@ -149,7 +149,7 @@ func (tree *BPlusTree) SplitRoot() {
 	// split the node in two
 	mid := len(root.keys) / 2
 	leftKeys := root.keys[:mid]
-	rightKeys := root.keys[mid:]
+	rightKeys := root.keys[mid+1:]
 
 	leftChildren := []*BPlusTreeNode{}
 	rightChildren := []*BPlusTreeNode{}
diff --git a/.archive/bplustree_test.go b/bplustree_test.go
similarity index 73%
rename from .archive/bplustree_test.go
rename to bplustree_test.go
index 75b7e26..af12299 100644
--- a/.archive/bplustree_test.go
+++ b/bplustree_test.go
@@ -79,9 +79,6 @@ func TestIsShapedCorrectlyAfter5(t *testing.T) {
 		tree.Insert(key, fmt.Sprintf("Node #%d", key))
 	}
 
-	tree.Print()
-	return
-
 	// root
 	assert.Equal(t, []int{3}, tree.root.keys)
 
@@ -91,12 +88,40 @@ func TestIsShapedCorrectlyAfter5(t *testing.T) {
 
 	// 3rd layer
 	// left
-	assert.Equal(t, []int{1}, tree.root.children[0].children[0])
-	assert.Equal(t, []int{2}, tree.root.children[0].children[1])
+	assert.Equal(t, []int{1}, tree.root.children[0].children[0].keys)
+	assert.Equal(t, []int{2}, tree.root.children[0].children[1].keys)
+
+	// right
+	assert.Equal(t, []int{3}, tree.root.children[1].children[0].keys)
+	assert.Equal(t, []int{4, 5}, tree.root.children[1].children[1].keys)
+
+	tree.Print()
+}
+
+func TestIsShapedCorrectlyAfter6(t *testing.T) {
+	tree := NewBPlusTree(3)
+	keys := []int{1, 2, 3, 4, 5, 6}
+
+	for _, key := range keys {
+		tree.Insert(key, fmt.Sprintf("Node #%d", key))
+	}
+
+	// root
+	assert.Equal(t, []int{3}, tree.root.keys)
+
+	// 2nd layer
+	assert.Equal(t, []int{2}, tree.root.children[0].keys)    // right
+	assert.Equal(t, []int{4, 5}, tree.root.children[1].keys) // left
+
+	// 3rd layer
+	// left
+	assert.Equal(t, []int{1}, tree.root.children[0].children[0].keys)
+	assert.Equal(t, []int{2}, tree.root.children[0].children[1].keys)
 
 	// right
-	assert.Equal(t, []int{3}, tree.root.children[1].children[0])
-	assert.Equal(t, []int{4, 5}, tree.root.children[1].children[1])
+	assert.Equal(t, []int{3}, tree.root.children[1].children[0].keys)
+	assert.Equal(t, []int{4}, tree.root.children[1].children[1].keys)
+	assert.Equal(t, []int{5, 6}, tree.root.children[1].children[2].keys)
 
 	tree.Print()
 }