Design Guidelines

These design guidelines are key rules that, if followed, will help you create code that is easy to develop and to maintain.

• Practice test-driven development. Before you write any code, write an automated test that tests if that code works. Use this for new features as well as bug fixes.

• Include automated unit tests. A unit test tests an internal part of the code, such as a method. A method is a contract: given certain assumptions about the data used by the method, the method is guaranteed to produce certain data. A good rule of thumb is to have at least one unit test for every contract of every method. As always, use your judgment as to what tests to write.

• Include automated acceptance tests.

• Never duplicate code. Avoiding duplication results in lots of good, such as decoupled designs.

• Favor composition over inheritance.

• If you can think of a reason you want to use different versions of a method, convert the method to an class and use composition.

• Relentlessly keep your abstractions current with your understanding of the system.

• Have an abstraction for every ``real world'' object that the modeler interacts with, e.g. ``a run request,'' ``a queue of run requests,'' etc.

• Create decoupled designs. A class C should only know about another class B when C's abstraction requires knowledge of B.