I bet that Spock needs not to be introduced to anyone here. For many of us it was an entry point to the thrilling world of Groovy. Spock has a flat learning curve - a sensible Java programmer (without prior Groovy experience) can start writing Spock specifications within several minutes. However, when you combine Groovy & Spock magic, a new fascinating meta-world is created. The exploration of its every nook and cranny can take much longer (and it's definitely much more efficient with a guide ;-).
You can expect a set of more advanced (and/or less known) techniques and mechanisms, the use of which can even more simplify and facilitate the testing of our code. You have to be forewarned that we will also visit those dark areas where it is better not to enter, things that do not work or work in a way nobody expects.
Spoiler. It is a Groovy focused version of my warmly welcomed "Smarter testing Java code with Spock Framework" presentation, enriched with additional tricks and traps.