Divergent Change smells occur when a single class needs to be edited many times when changes are made outside the class.
class Fish: def __init__(self, id, aquarium): self.name = aquarium.get_fish_name(id) # Overly reliant on aquarium's method
The consequence of this is that you can easily cause errors whenever a change is made that the class does not expect, limiting how quickly you can make changes to the code.
The aim should be that changes and classes should have a one-to-one relationship (each change affects only one class). Divergent Change smells are many-to-one (many changes affect one class).
In principle, a class should be self-sufficient. It should not need outside code to work in a particular way.
Divergent Change is the opposite of Shotgun Surgery.