XML maven artifact not on classpath - maven

Question

I have some external configuration (XML files) that are installed in Maven. I need to have them on my test classpath but they aren't appearing.
They must stay as XML, I cannot package them inside a Jar - but I am willing to try anything else for this, custom plugin etc.
(Please don't inform me that Maven is only for Jars - that's simply not true (and if you provide a reference refuting that I can assure you it's out-of-date/misinformation).
The dependencies are specified thus:
<dependency>
<groupId>some.group</groupId>
<artifactId>some.artifact</artifactId>
<version>${project.version}</version>
<scope>test</scope>
<type>xml</type>
<classifier>some.classifier</classifier>
</dependency>
These XML artifacts have been created by the build-helper plugin (so there's no 1-2-1 with their project's POM).
My only current hacky solution is to, check for the M2_HOME property and load the files from there (as they're defined as dependencies Maven does pull them down) - but I'm not happy with this.
EDIT: The next best hack is probably to use the maven-dependency-plugin to copy these to the output directory (target/classes). If my config is fine for Jars then this smells like a Maven bug.
EDIT 2: #khmarbaise asked for the build-helper-plugin config:
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>build-helper-maven-plugin</artifactId>
<executions>
<execution>
<id>attach-artifacts</id>
<phase>package</phase>
<goals>
<goal>attach-artifact</goal>
</goals>
<configuration>
<artifacts>
<artifact>
<file>target/classes/ddl-seed.xml</file>
<type>xml</type>
<classifier>ddl-seed</classifier>
</artifact>
<!-- ... more definitions -->
This generates the correct maven-metadata-local.xml data for all the XML artifacts.

Answer 1

Unfortunately I can find no way of forcing maven to add the test dependency specified to the test classpath, other than this stinky hack of copying it to a directory on the test classpath.
This seems the quickest way (it's for a test dependency), avoiding any JAR creation.
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<executions>
<execution>
<id>unpack</id>
<phase>generate-test-resources</phase>
<goals>
<goal>copy</goal>
</goals>
<configuration>
<artifactItems>
<artifactItem>
<groupId>com.acme.gid</groupId>
<artifactId>com.acme.aid</artifactId>
<version>${project.version}</version>
<classifier>ddl</classifier>
<type>xml</type>
<outputDirectory>${project.build.directory}/test-classes</outputDirectory>
</artifactItem>
</artifactItems>
</configuration>
</execution>
</executions>
</plugin>