unit tests for the cumulative scope filter, and integration tests for the default project dependencies resolver. Mocking the resolver got pretty ugly, so I'm falling back to ITs for this for now, since they're easy to understand, even if they are a little more prone to underlying problems in dependencies.
maven/shared/trunk/maven-artifact-resolver/pom.xml
maven/shared/trunk/maven-artifact-resolver/src/test/java/org/apache/maven/shared/artifact/resolver/testutil/