There are actually some standardized tests that work for animals, at least. Self-recognition is one - be it in a mirror, in playbacks of calls, etc.
Ah, I thought there might be. But I wonder if those tests are just designed so they'll work for animals that we already assume are conscious?
No. In fact, they were originally developed as a means of gaging mental retardation and other mental defects in humans. Much of the recent development has been in trying to move these tests away from a human-centric concept of self awareness to a more generic one, applicable to anything from animals to computers.
-Is the object aware of time,
-Is the object aware it is separate from the environment,
-Is the object aware of other similar objects in its environment (i.e. other members of its own species),
-Is the object aware it is separate from its fellow species (etc) members,
-Does the object show an awareness of death,
An animal/entity that has no way to communicate, other than by us directly observing its internal workings, would surely be pretty hard to test.
For things like animals, much can be inferred from behavior. Chimps, for example, mourn their dead. That's pretty clear evidence that they are aware of death, and the finiteness of their existence.