polymorphism ~ strategy

polymorphism.java

interface DatabaseAccess {
  void save(Object entity);
}

class MySQL implements DatabaseAccess{
  @Override
  void save(Object entity) {
    //saving obj into MySQL
  }
}

class UserService {
  DatabaseAccess db;
  
  UserService(DatabaseAccess db) {
    this.db = db;
  }
  
  void saveUser(User u){
    db.save(u);
  }
}


---------- TEST -----------
  
class DatabaseAccessMock implements DatabaseAccess{
  @Override
  void save(Object entity) {
    //mocking insert
  }
}

class UserServiceTest {
  void test_save_user(){
    UserService service = new UserService(new DatabaseAccessMock());
    service.save(new User(...));
  }
}