Unfortunately, seems the only way to figure this out is by testing. But on the flip, nobody can really trust that it won't accidentally or purposefully escape from labs.
Remember, no one has built a regular cell from scratch, much less come close to building a mirror cell.
E.g.
https://en.wikipedia.org/wiki/1971_Aral_smallpox_incident
https://www.fredericknewspost.com/archives/what-went-wrong/a...
https://www.nytimes.com/2004/05/25/world/russian-scientist-d...
https://www.usatoday.com/story/news/nation/2015/07/23/army-a...