If you create a new, empty MDB, and then import the tables from the old one,
there is an option to import only the definition of tables, not the data. To
see this option, click the 'Options' button in the Import Objects dialog
box.
An alternative is to write a bunch of queries to delete the test data, and
if you have a lot of tables, you'll want to write some code to execute those
queries one after another. This takes a little work initially, but has the
advantage that once done you can re-use it as often as necessary.