--- a/main.lua	Tue Sep 11 21:16:00 2018 +0100
+++ b/main.lua	Tue Sep 11 21:25:40 2018 +0100
@@ -313,4 +313,11 @@
 
 log_data("end", { time = time(), summary = result_tally });
 
+local exit_code = 0;
+if result_tally.error then
+	exit_code = 2;
+elseif result_tally.fail then
+	exit_code = 1;
+end
+
 os.exit(exit_code);