What enemies does Bilbo Baggins encounter and how is he tested?

In "The Hobbit," Bilbo Baggins encounters several enemies, including trolls, goblins, and the dragon Smaug. Each encounter tests his courage, cleverness, and resourcefulness. For instance, he uses his wits to outsmart the trolls and escape from the goblins in their underground lair. His ultimate test comes when he confronts Smaug, where he must rely on his intelligence and bravery to negotiate and survive.