diff -r 5f36d04d23a5 -r 5dcc339114f7 cws/cw05.tex
--- a/cws/cw05.tex	Thu Dec 06 18:37:17 2018 +0000
+++ b/cws/cw05.tex	Thu Dec 06 18:50:53 2018 +0000
@@ -463,7 +463,16 @@
   worthwhile overall (of course for the \pcode{>A}'s and so on, the compiler incurs a
   penalty). Luckily, after you have performed all
   optimisations in (5) - (7), you can expect that the
-  \pcode{benchmark.bf} program runs four to five times faster.\hfill{[2 Marks]}
+  \pcode{benchmark.bf} program runs four to five times faster.
+  You can also test whether your compiler produces the correct result
+  by for example testing
+
+  \begin{center}
+  \pcode{run(load_bff("sierpinski.bf")) == run4(load_bff("sierpinski.bf"))}
+  \end{center}
+
+  which should return true for all the different compiler stages. \\ 
+  \mbox{}\hfill{[2 Marks]}
 \end{itemize}  
 
 \end{document}