added Testing section

README

@@ -6,7 +6,7 @@ implement them.
 			19th March 2002
 
 Building and Packaging on Linux
------------------
+-------------------------------
 
 Either download http://csgsoft.doc.ic.ac.uk/datadec/datadec-1.0-1.i386.rpm
 and install it (rpm -i) from there, or do a source build:
@@ -52,3 +52,15 @@ Building on Solaris or Other Unices
 5. install the package (as root):
 
 	pkgadd -d datadec-1.0-1-sol8-sparc-dcw all
+
+
+Testing
+-------
+
+Having built datadec in the source directory, you can also compile and
+run a test harness in the test directory.  test/cdata.in is the datadec
+input file which declares some recursive data types (lists and trees),
+and ctest.c is the test harness that uses them.  cd into test and run make
+to turn cdata.in into cx.h and cx.c, and to compile cx.c and ctest.c and
+link them..
+