diff --git a/todo.md b/todo.md
index 405085d..1089d84 100644
--- a/todo.md
+++ b/todo.md
@@ -2,4 +2,6 @@
 - Line number display
 - Editor info display (filename, current line/column, indentation style, etc.)
 - File opening by entering path
-- UI that wraps editors, for split view.
\ No newline at end of file
+- UI that wraps editors, for split view.
+- Unit testing for text block, text node, and text buffer.  They must
+  be reliable!
\ No newline at end of file