I assume you’ve read the docs about running a single test under surefire? What they don’t tell you is how to do that in a sub-module:
mvn test -Dtest=testname -pl subproject
Where subproject is the project containing that test. From the mvn man page:
-pl,–projects arg Comma-delimited list of specified reactor projects to build instead of all projects. A project can be specified by [groupId]:artifactId or by its relative path.