a dry run
A practice session or test designed to identify and correct possible problems. Let's do a couple dry runs of your speech so you feel totally comfortable with it for tomorrow's ceremony. The theater group did a dry run of the play to iron out any technical problems before opening night.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
a dry runor
a test run
A dry run or a test run is something that you do to practise before you do it at a more important time. We'll have a dry run at getting you in and out of the clothes quickly. More than 10,000 people were expected and council chiefs said it would be a dry run for the Olympic celebrations.
Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012