There are public companies in the industry. All are highly risky/volatile stocks, though. Nothing like a blue chip company yet, which you could trust to steadily rise in tandem with the industry.

I think there are only few labs specialized in testing THC and CBD levels yet. While it isn't very hard to grow or create other products, I don't think it's easy to compete with a service like this.

Wouldn't a huge industrial testing company eventually decide the market is big and safe enough to enter and just crush the small players on scale?

There are definitely investment channels. Beware though, the feds could come down at any moment. Some percentage of the money you invest in the stocks should also go to political lobbying to prevent heavy regulation.

I'm working on a product for it currently in California. Email me if you're interested in talking.