In this video,Peter Bell explains DSLs, how to approach writing one, and especially how to evolve one over time using “fixing the API”, “backwards compatibility”, “versioning” and “automated evolution/checking”.
http://www.infoq.com/presentations/DSL-Evolution-for-Groovy-Developers

This video shows how to use Spock testing specifications and Groovy for mocking and stubbing behavior in unit tests. It covers creating the mock object syntax, setting expectations, verifying and spying on results, and argument matchers.

This Grails video covers the following topics:
* Java and Groovy Code differences.
* Putting Java classes in a Grails Application.
* Controllers & Closures.
* How a URL from the user triggers a Controller / Closure.

This video reviews the main features brought by Groovy 1.6 like better performance, multiple assignments, optional return, AST transformations, Grape, OSGi, etc. It discusses also what is most interesting and new in Groovy 1.7: anonymous classes, annotations, power asserts, AST viewer and builder. Finally, it presents Groovy 1.8: closures, modularization, Java 7 support, DSL, AST templates, better performance.
http://www.infoq.com/presentations/Groovy-Update

This is the first tutorial of an ongoing series of basic introductory lessons on using the Grails Framework.

Video producer: http://grails.org/screencast/show/24

This screencast demonstrates how to create Spock testing specifications. It covers creating basic when/then blocks, given/when/then blocks, expect/where blocks, and data tables.

Cucumber isn’t a tool exclusively for the Ruby world. The JVM is a very popular development platform and you can leverage your existing skills by automating your scenarios with Java or its expressive by closely related brother Groovy. This talk includes automating Cucumber scenarios with Groovy, from writing step definitions, working with tables, to exposing commonly used functionality with Cucumber’s World mixin. Driving acceptance tests with Geb (a Groovy DSL for Selenium) will get you started with automating your scenarios through a browser.
http://skillsmatter.com/podcast/agile-scrum/cuke-groovy