Add unit test for method create_tree() from Index class

test/test_index.py

@@ -88,6 +88,13 @@ class IndexTest(utils.RepoTestCase):
         index.read()
         self.assertTrue('bye.txt' in index)
 
+    def test_create_tree(self):
+        sha = 'fd937514cb799514d4b81bb24c5fcfeb6472b245'
+        index = self.repo.index
+        index.read()
+        tree = index.create_tree()
+        self.assertEqual(sha, tree.sha)
+
 
 if __name__ == '__main__':
     unittest.main()