How often in your code do you see ifs checking whether the object is not null? Often? Very often? What would happen if you didn’t have to check it out? Surely code would be easier to maintain – no ifs = no test cases. This can all be achieved using Null Object pattern.
Null Object pattern should be used as a substitute for objects which don’t exists in the runtime or you don’t know current state of the object. You may apply it, however, bear in mind that it’s not suitable for all test scenarios. You’ve to analyze whether it’s a good idea to use it.