If you are interested in seeing an application which is pre-built which also incorporates the Grails specific testing practices and approaches (as well as some widely practised testing methods as used within Grails), the Winelovers application outlines a fully working app and a number of different testing angles which can be applied to create confidence and increase testing coverage for your apps.
https://svn.energizedwork.com/skunkworks/grails/WineLovers/
There is also a presentation which accompanies this which goes into samples and pros and cons.
I will be following up this work with a greater number of examples and further tutorial type updates to help draw out the benefits of testing this way and this much.
