Wiktionary
dummy runs
n. (dummy run English)
Usage examples of "dummy runs".
Libby was fascinated and soon was putting himself through dummy runs.
But he did so well at the dummy runs that by the fifth day they were putting him on the late news to do ninety-second capsule reports in what they called the mosaic-texture section, in which a bunch of broadcasters offered quick bouncy segments of the news in swift succession.