diff --git a/TODO b/TODO
index beccfb90d952b4f977b6689cf3a61696f45125d2..0042953272d6795286c3e818e988a9f9cfaab34a 100644
--- a/TODO
+++ b/TODO
@@ -129,6 +129,8 @@ Roughly in order of importance.                                     -*-org-*-
 
 * Implement a pretty printer for lists/tuples of sites
 
+* Ensure 100% test coverage
+
 * Ideas for kwant 2
 ** Consider whether to use *args or args in System.hamiltonian