Initially, I had my hibernate.cfg.xml file in the following directory

my-app/src/main/java

And when I first tried to run my hibernate unit tests (mvn test), I got this error:

SessionFactory creation failed.org.hibernate.HibernateException: /hibernate.cfg.xml not found

Some checking of the maven docs and some forums revealed the following possible solutions:
1) Copy the hibernate.cfg.xml file to

my-app/target/classes

This works, however I think it is a hack as the target folder is generated rather than being somewhere you should actually manually create files.
2) The next solution I found suggested moving the hibernate.cfg.xml to

my-app/src/main/resources

This works well as the contents of this folder are copied to the base level of the my-app/target/classes folder so it is basically a ‘more correct’ solution than the first.
3) The next and I think best solution was to create a new, duplicate hibernate.cfg.xml inside

my-app/src/test/resources

This allows a different hibernate.cfg.xml file to be used for testing and, for example, facilitates connecting to a different database (such as hsqldb) for testing while continuing to use your regular database (such as MySQL) for the app itself.

A couple of points to note:

1) The hibernate mapping files (i.e. the *.hbm.xml files) should also be in the resources folder (in whatever directory structure you choose) to ensure that these too are accessible by the unit tests.

2) I am not (yet) using Spring with the hibernate components, which would likely have changed the above setup.

Refs/links

http://maven.apache.org/guides/getting-started/index.html#How_do_I_add_resources_to_my_JAR

http://www.mail-archive.com/users@maven.apache.org/msg54720.html