Inheritance, polymorphism and regression testing

The following diagram shows examples of both inheritance and polymorphism.

You can select between creating SAVINGS_ACCOUNT object and a CHEQUE_ACCOUNT by clicking on the appropriate cross. Similarly, you can also select between creating a super class reference to the object or a sub class reference to the object. Clicking on the display or show_balance function will cause the appropriate Eiffel code to generated and displayed, along with the code output.

Although not shown in the diagram, the display method of the SAVINGS_ACCOUNT and CHEQUE_ACCOUNT displays is simple "Hello..." message as well as the current balance. The ACCOUNT show_balance method simply displays the balance.

 

So how does this tie into inheritance regression testing? Easy. If you have written a test case to test the show_balance method of the ACCOUNT class, you can reuse this test to use the SAVINGS_ACCOUNT and CHEQUE_ACCOUNT classes.