Swollen hose
A good test for a hose is to feel it for softness and porosity. Often these defects show up as swollen spots on the hose. The most likely cause is oil exposure. The hose can burst at any time when heated and under pressure.
Cracked hose
Cracked hoses appear due to the fact that they usually just inspect the hoses, but do not feel if they are hard.
Hose end wear (due to weak grip)
Loose clamps are often the cause of damage to coolant hoses. The tube-hose connection wears out and fluid flows out when the engine is hot.
Dirt in the cooling system
Dirt, rust and scale in the cooling system will cause wear on the inside of the hose. It can be felt from the outside as a soft or sophisticated place.