Is using one-to-one interfaces with domain entities a good or bad practice? Why?

Question

One thing I see in some DDD enterprise apps that I work on, is the use of interfaces that are identical to the domain entities, with a one-to-one mapping of properties and funct

Answer 1

In general, if my classes are not going to be part of a design pattern like Strategy or Visitor I don't add interfaces.

Adding interfaces is really useful for design patterns like Strategy and Visitor, but in those cases I don't carbon copy the getters and setters of the domain classes. Instead, I create interfaces that are specific for the design pattern interfaces I create.

interface SomeStrategy {
   void doSomething(StrategyData data);
}

interface StrategyData {
   String getProperty1();

   String getProperty2();
} 

That allows me to let the domain classes implement those interfaces, or to use the Adaptor pattern. I find this is a much cleaner approach that just creating interfaces for the sake of it.

Design should always reduce uncertainty. Creating interfaces for the sake of it doesn't reduce uncertainty, in fact it probably increases confusion since it doesn't make any sense.