Grigor Avagyan shows how to test an API endpoint with Spock and explains every line involved in the specification. You will immediately see one big advantage of Spock; succinctness. Another key feature of Spock is the use of JUnit Runner.
Another big pro for Spock is that it uses the JUnit runner. This means that if you’ve already been running your tests with it, you can keep doing so, and you don’t need to learn how to use a new runner! In addition, this makes your tests compatible with all existing JUnit tools.