How to access test resources in Scala?

Resources are meant to be accessed using the special getResource style methods that Java provides. Given your example of data.xml being in $SBT_PROJECT_HOME/src/test/resources/, you can access it in a test like so:

import scala.io.Source

// The string argument given to getResource is a path relative to
// the resources directory.
val source = Source.fromURL(getClass.getResource("/data.xml"))

Of course that source is now just a normal Scala IO object so you can do anything you want with it, like reading the contents and using it for test data.

There are other methods to get the resource as well (for example as a stream). For more information look at the getResource methods on the Java Docs: Class.