away from an inheritance-based mechanism we no longer
had an easy way for others to extend NUnit's internal behavior. NUnit Addins are
intended to fill that gap, providing an mechanism to introduce new or changed
behavior without modifying NUnit itself.</p>

<h3>Extension Points, Extensions and Addins</h3>

<p>NUnit provides a number of <b>Extension Points</b>, places where it is
possible to extend its behavior. Because NUnit works with various hosts
and uses separate AppDomains to run tests, <b>Extension P