[cddlm] CDL tests for expressions

[Steve Loughran]

Do we have any tests for expressions yet? I dont see any in CVS?

If anyone has written any for their own implementations, please stick 
them into the repository, in the expressions/ package(s).

On a related note, I now have lazy references working, although the 
relevant tests are still failing. I'm not generating the correct XML 
representation for the XML comparision to work, but instead converting 
straight to a classic smartfrog lazy reference chain. The only way to 
reliably test these would be to have an assertion component that checks 
two strings for being equal

<assert:assertEquals>
   <expected>expected</expected>
   <actual cdl:ref="/something" cdl:lazy="true" />
</assert:assertEquals>

<something>expected</something>

We could use this for expression testing too, obviously.

-steve