| Clue | Source | Date |
|---|---|---|
| First attempts at doing things to make sure they can be done properly (5,4) (5,4) | ||
| Initial tryouts | USA Today | 19 Mar 2024 |
| Test drives | New York Times | 03 Feb 2024 |
| Tests | New York Times | 03 Jul 2021 |
| Tests | LA Times Daily | 27 Mar 2021 |
| Tests | The Washington Post | 27 Mar 2021 |
| Tests of performance | Wall Street Journal | 05 Nov 2019 |
| Tests of performance | ||
| Test drives | Eugene Sheffer | 15 Jan 2018 |
| Preliminary tests | ||
| Initial tests | ||
| Testing sessions |