Test involves putting a paint mark on a subject of any species, and seeing if it tries to clean the mark when in front of a mirror as a mark of self-awareness.
Except the reasoning behind this seems a little too convoluted. Cleaning up might mean having a visual image of the self and what does not belong, but we already have a plethora of receptors and senses dedicated to that. It does not seem to fit Occam's razor to prioritize a tiny bit of visual stimulus from the skin over hundreds of receptors located there as mapping into a construction of the self.
A better association seems to be with self-identity, where the emphasis on maintaining an image others see. Which even better explains why an ant can pass the MSR test but not a cat.
So why is the consensus associating it with self-awareness instead?