. Two approaches used to write the specifications for operations between a sender and a receiver object (e.g., Queue) are based on design by contract and defensive design.

1. Briefly describe each of the two approaches to writing such a specification.
2. State how each approach affects the testing process and relate it to a Queue class where possible.
3. Draw a state machine specifying the operations for a Queue using the defensive design approach. Use a modeling tool, such as StarUML, to draw your state machine (statechart), copy and paste the state machine into this document.