diff --git a/src/functions.php b/src/functions.php
index be14bca28f21cfba344c1d6a4c1be8eb0470aec1..533a41cadc8d344cbd9a2ae7b6a6db9967692aac 100644
--- a/src/functions.php
+++ b/src/functions.php
@@ -5,6 +5,7 @@
 
 // todo: TESTS: better assertion messages + throw FunctionSignatureAssertionError + catch in fn + pass it to assert -> compatible with PHP assert config
 // todo: covariance and contra-variance
+// todo: tests for primitive types
 
 namespace Grifart\AssertFunction;