Wiktionary
trial balloons
n. (trial balloon English)
Usage examples of "trial balloons".
All these trial balloons make their way into the average cost of a book.
Seems to me you've been floating trial balloons for quite a while.
But before you start complaining, let me warn you: the cost of these trial balloons is minimal compared to everything else you're paying for when you slap down your $24.
We send up trial balloons all the time, feeling each other out on a justice’.