diff --git a/source/simple/support/array_operators.hpp b/source/simple/support/array_operators.hpp
index bf2ed96b2460ad2feb0b1db4c15c4a1ac3f740b8..49db9b99e6de4837aa0706345d801537d5f2ac8f 100644
--- a/source/simple/support/array_operators.hpp
+++ b/source/simple/support/array_operators.hpp
@@ -281,6 +281,7 @@ namespace simple::support
 		// this is the another thing you need in order to support type promotion, expression templates etc.
 		// you can set this to the shape of the array (which would be size if there is no nesting),
 		// along with a tag that identifies the template, if you want that extra safety
+		// TODO: this is about operands so include operand in the name, perhaps simply operand_tag
 		using compatibility_tag = Type;
 	};
 
diff --git a/unit_tests/math.cpp b/unit_tests/math.cpp
index a9d653d852963007d16ce06fcf632f6f9af5a501..9f3c20338e713ec94166115d139fb64ab051239c 100644
--- a/unit_tests/math.cpp
+++ b/unit_tests/math.cpp
@@ -1,3 +1,5 @@
+// TODO: need a test file per header and include the header first, to detect missing includes
+
 #include <cassert>
 #include <random>
 #include <iostream>
diff --git a/unit_tests/random.cpp b/unit_tests/random.cpp
index b4f54089a2a705f4635f1ca2074c850dbd9aebd1..6f0df6427bb9d4cf8e702866aa29406d573adae5 100644
--- a/unit_tests/random.cpp
+++ b/unit_tests/random.cpp
@@ -1,3 +1,5 @@
+// TODO: need a test file per header and include the header first, to detect missing includes
+
 #include <iostream>
 #include <sstream>
 #include <cassert>
diff --git a/unit_tests/tuple_utils.cpp b/unit_tests/tuple_utils.cpp
index 1299a61d15d385d784268f8bbd68cb0c69b3359f..19318146b3e361159da17697811e3a85c8ebf6f0 100644
--- a/unit_tests/tuple_utils.cpp
+++ b/unit_tests/tuple_utils.cpp
@@ -1,3 +1,5 @@
+// TODO: need a test file per header and include the header first, to detect missing includes
+
 #include <cassert>
 #include <string>
 #include <sstream>