Benjamin checked in a classpath ordering test in the Surefire trunk that we now run with every release. It's currently passing in Surefire 2.4.2 and Maven 2.0.8, and failing with Maven 2.0.7.
Still having problems?
Read this page, which explains how Surefire launches your tests. Classloading and Forking under Maven Surefire
Also, take a look at this Nabble discussion. (Mostly redundant, but it couldn't hurt.) http://www.nabble.com/Surefire-2.4.1-classpath-order-td15498825s177.html