Commit 74a52d2

@@ -0,0 +1,26 @@
+#include "avl_tree.h"
+#include <stdlib.h>
+
+AVLNode *avl_node_init(int value) {
+  AVLNode *node = malloc(sizeof(AVLNode));
+  node->left = NULL;
+  node->right = NULL;
+  node->value = value;
+  return node;
+}
+
+AVLTree *avl_tree_init() {
+  AVLTree *tree = malloc(sizeof(AVLTree));
+  return tree;
+}
+
+int avl_tree_size(AVLTree *tree) {
+  if (tree->root)
+    return 1;
+  else
+    return 0;
+}
+
+void avl_tree_insert(AVLTree *tree, int value) {
+  tree->root = avl_node_init(value);
+}

@@ -0,0 +1,13 @@
+typedef struct node {
+  struct node *left;
+  struct node *right;
+  int value;
+} AVLNode;
+
+typedef struct {
+  AVLNode *root;
+} AVLTree;
+
+AVLTree *avl_tree_init(void);
+int avl_tree_size(AVLTree *tree);
+void avl_tree_insert(AVLTree *tree, int value);

@@ -3,12 +3,28 @@
 #include <string.h>
 
 Ensure(initialize_returns_new_tree) {
-  assert_that(NULL, is_equal_to(NULL));
+  AVLTree *tree = avl_tree_init();
+  assert_that(tree, is_not_equal_to(NULL));
+}
+
+Ensure(size_returns_zero) {
+  AVLTree *tree = avl_tree_init();
+
+  assert_that(avl_tree_size(tree), is_equal_to(0));
+}
+
+Ensure(insert_changes_size) {
+  AVLTree *tree = avl_tree_init();
+  avl_tree_insert(tree, 33);
+
+  assert_that(avl_tree_size(tree), is_equal_to(1));
 }
 
 TestSuite *avl_tree_tests() {
   TestSuite *suite = create_test_suite();
   add_test(suite, initialize_returns_new_tree);
+  add_test(suite, size_returns_zero);
+  add_test(suite, insert_changes_size);
   return suite;
 }