Add (empty) section to documentation about running tests

Author: Owen Jones

doc/architectural/compilation-and-development.md

@@ -17,6 +17,10 @@ To be documented.
 
 To be documented.
 
+## Running tests
+
+To be documented. (regression tests with test.pl and unit tests with Catch.)
+
 ## Documentation
 
 Apart from the (user-orientated) CBMC user manual and this document, most