diff --git a/src/test/cli_argument_parser.cpp b/src/test/cli_argument_parser.cpp
index 94c71ff..fdabc70 100644
--- a/src/test/cli_argument_parser.cpp
+++ b/src/test/cli_argument_parser.cpp
@@ -186,5 +186,10 @@ int main(int argc, char* argv[]) {
     //TODO add tests for invalid input
     std::cerr << "TODO: invalid input tests" << std::endl;
 
+    // test cases for invalid input:
+    //  - unknown flags, arguments (mixed with other input and standalone)
+    //  - too few, too many positional arguments (mixed with other input and standalone)
+    //  - check the produced error messages
+
     return 0;
 }