Older Dog Not Eating and Vomiting?

We have a 14 year old dog that has always been healthy. He started eating less which we associated with age. The past week plus he stopped eating altogether. After a visit and overnight stay at the vet, all tests came back negative.

He is drinking OK, but we were only able to get a few spoons of food in him. About an hour ago he vomited a dark brown/black substance. We are just not sure if this is his time. We really don't want to put him through many more tests. He came home really depressed.