add include to test/benchmark config

test.cfg

@@ -12,6 +12,7 @@ primary {
   # Primary-sub stuff
   sub {
       key = "primary sub key value";
+      include "test_include.cfg";
   }
 }
 

test_include.cfg

@@ -0,0 +1 @@
+included_setting = "primary sub included_setting value";