How to 'Test BACC "Thumper" Solid Fuel Booster in flight over Kerbin'?

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After endless tries, how can it be achieved?
Req: 5Km~14Km, 100~800 m/sec
I created a craft with the device, achieved all test conditions (all is green), still I don't get the achievement. What did I miss?
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Sources: Stack Exchange - This article follows the attribution requirements of Stack Exchange and is licensed under CC BY-SA 3.0.
Images: Max Vakhtbovych, Monstera, César Coni, SpaceX