| <?xml version="1.0" encoding="UTF-8"?> |
| <org.eclipse.epf.uma:ContentDescription xmi:version="2.0" |
| xmlns:xmi="http://www.omg.org/XMI" xmlns:org.eclipse.epf.uma="http://www.eclipse.org/epf/uma/1.0.4/uma.ecore" |
| xmlns:epf="http://www.eclipse.org/epf" epf:version="1.2.0" xmi:id="-U8NScY6mORb4XPcNZ_mrEA" |
| name="refactoring_xp_programming,1.4410217108363206E-306" guid="-U8NScY6mORb4XPcNZ_mrEA" |
| changeDate="2006-11-09T19:20:46.023-0500" version="1.0.0"> |
| <mainDescription><a id="XE_xp__refactoring" name="XE_xp__refactoring"></a><a id="XE_refactoring__practice_of" name="XE_refactoring__practice_of"></a><a id="XE_engineering_practices__refactoring" name="XE_engineering_practices__refactoring"></a> 
 |
| <h3>
 |
| Description
 |
| </h3>
 |
| <p>
 |
| Refactoring is the practice of improving the design of a system without changing its behavior. Refactoring is a
 |
| critical practice and skill in iterative development. The programmer is either adding a new feature or refactoring. XP
 |
| programmers consciously choose between refactoring and adding new functionality on a minute-by-minute basis. Some
 |
| refactorings are trivial, such as renaming or moving things. Other refactorings allow you to exchange procedural logic
 |
| with polymorphism, and still larger refactorings exist to introduce design patterns.
 |
| </p>
 |
| <p>
 |
| While processes like Extreme Programming rely on refactoring to let the design emerge, the usefulness of refactoring
 |
| extends beyond the Agile Methodologies. As feature requests and bug fixes require changes to a system, refactoring
 |
| techniques allow the programmers to maintain a good design. Refactoring can also be used to improve the design of an
 |
| existing system.
 |
| </p>
 |
| <p>
 |
| Refactoring is not new. Developers have been refactoring for years, though only recently have people started to catalog
 |
| refactorings. Refactoring has become such an important part of development that professional-level Integrated
 |
| Development Environments (IDEs) either include built-in tools or have plug-ins to provide refactoring support.
 |
| </p>
 |
| <p>
 |
| If your system isn't being refactored as it is modified, your design deteriorates; methods become longer, classes take
 |
| on more responsibility, more code gets cut and pasted around your system, previously cut-and-pasted code has to be
 |
| modified in several places.
 |
| </p>
 |
| <p>
 |
| If your system becomes brittle and inflexible, your developers will have to spend more time and money to add features
 |
| or fix bugs. As the design continues to deteriorate, fixing one bug creates two more, or the cost of adding a new
 |
| feature out weighs the benefit of having it because so much of the system has to be modified. There are many analogies
 |
| to describe this battle against entropy; from cleaning as you go to design debt.
 |
| </p>
 |
| <p>
 |
| Knowing the refactorings isn't enough. Developers must be able to identify problem areas of the program design (often
 |
| referred to as "smells"). These are the places where refactoring can be used to improve the design of the code. Design
 |
| skill and experience are needed to recognize bad code smells.
 |
| </p>
 |
| <p>
 |
| Automated tests provide a safety net when making changes. The automated tests report when the functionality of the
 |
| system changes. Make a structural change to the software; see that the tests still pass. You can confidently refactor.
 |
| </p>
 |
| <p>
 |
| Where do all these tests come from? In XP, they are developed using <a class="elementLinkWithUserText" href="./../../../xp/guidances/concepts/test_driven_development.html" guid="1.620567348185129E-306">Test-Driven Development</a>. It is possible to refactor without tests, but you run the
 |
| risk of unknowingly introducing bugs or breaking existing functionality.
 |
| </p>
 |
| <h3>
 |
| Benefits
 |
| </h3>
 |
| <ul>
 |
| <li>
 |
| Allows the design to emerge over time.
 |
| </li>
 |
| <li>
 |
| Keeps the design from rotting.
 |
| </li>
 |
| <li>
 |
| Reduces cost of change.
 |
| </li>
 |
| </ul>
 |
| <h3>
 |
| Related Information
 |
| </h3>
 |
| <p>
 |
| &nbsp;See the <a class="elementLinkWithUserText" href="./../../../xp/guidances/guidelines/refactoring.html" guid="8.137126904637637E-306">Refactoring Guidelines</a>.
 |
| </p></mainDescription> |
| </org.eclipse.epf.uma:ContentDescription> |
