The "camera test" for yuri (and I mean most lesbian media, I suppose):
If the two girls on the cover are looking at the "camera", then it's probably male-gazey claptrap targeted at straight men. Anime girls looking at the camera has connotations of "hey assumed-to-be-cisallohet-male audience, come look at us!" -- like that's implicitly "their priority", on a meta level. You are supposed to ogle them.
On the other hand, if the the two girls on the cover are looking at each other, then it's probably not male-gazey claptrap targeted at straight men. On the aforementioned meta level, their priority is each other, they don't care about the dudes. You are supposed to identify with them.