a dummy run

dummy run

A trial or practice version of an event, done to prepare for (and mitigate any possible problems during) the real thing. Primarily heard in UK, Australia. Let's do a couple dummy runs of your speech so you feel totally comfortable with it for tomorrow's ceremony.
See also: dummy, run

a dummy run

BRITISH
A dummy run is an occasion before an important event when you practise doing something, in order to make sure that it will be successful when you do it properly. Before we started, we did a dummy run, checking out all the streets and offices we would use, and planning our escape route. If it is not possible to do a dummy run in the hire car, calculate how long the journey to the church will take on the day.
See also: dummy, run