How can you tell when Durian fruit is rotten?

A coworker brought some Durian (“King of Fruits”) to work as a joke to try to gross everyone out with the powerful stench that is characteristic of this fruit. I pretended that I liked the smell and asked if I could eat some of the fruit even though I was a bit overwhelmed by the smell. To everyones horror I ate two pieces of the Durian. I didn’t lie when I said that I liked the taste. I liked it so much that the next day I bought some Durian and have been eating it up. To me it smells like rotting fruit so I wonder how to determine it the fruit is rotten.