This page is a script (of sorts) for how to do all the various eclipse settings needed, and do them "the hard way", by hand, from a clean eclipse install.
The following is the script for creating the XML settings
(Please improve this)
Scala as a language does not require file names to match class names, nor file directory paths to match package names.
However, the Eclipse IDE support for scala as of Scala IDE 3.0.0 (2014-04-04), allows class names to differ from file names, but is very dependent on directory structure matching the package structure. Without this unit tests will not be found, and so cannot be conveniently run from the IDE. (Error: No tests found for Junit... If you get this error, assume package and folder structure are not matching.)