I encourage you to read the detailed documentation for both these tools at their respective sites. The Gradle DSL has full and comprehensive documentation hosted at http://www.gradle.org/docs/current/dsl/index.html. A detailed documentation on Spock can be found at http://spockframework.github.io/spock/docs/1.0/index.html.

As further reading take a look at the ChapterThreeGradleSpec.groovy example in the code sources. Most of the Gradle examples from the start of the chapter are asserted via Spock feature methods in this specification. Now, take the time to explore the sample code associated with the book. Spock is used extensively to illustrate and assert the code examples in the book. Gradle is used as the primary build tool for building all the examples in the book.