Cucumber vs Spock comparison of testing frameworks
What are the differences between Cucumber and Spock?

	Cucumber https://github.com/cucumber/cucumber-ruby	Spock http://spockframework.org/
Programming language	Ruby	Java
Category	Acceptance Testing	Unit Testing
General info	An automation tool for Behavior-Driven Development The specifications are written in plain texts, which allows them to be easily understandable for all stakeholders. Cucumber Framework also supports languages beyond Ruby e.g. Java, JavaScript and Scala.	Spock is a testing and specification framework for Java and Groovy applications Spock has a highly expressive specification language, and due to its JUnit runner, Spock is compatible with most IDEs, build tools, and continuous integration servers.Spock is inspired from JUnit, RSpec, jMock, Mockito, Groovy, Scala, Vulcans among others
xUnit Set of frameworks originating from SUnit (Smalltalk's testing framework). They share similar structure and functionality.	No	No
Client-side Allows testing code execution on the client, such as a web browser	Yes You can test the front-end part like the GUI using cucumber and selenium, they integrate well to test your front-end.	Yes Spock tests front-end components and functionality by unit testing individual classes and functions
Server-side Allows testing the bahovior of a server-side code	Yes You can test back-end components such as APIs using rest & soap clients, and databases using whatever client libraries were provided by the libraries that existed in those stacks	Yes Spock tests back-end components and functionality by unit testing individual classes and functions
Fixtures Allows defining a fixed, specific states of data (fixtures) that are test-local. This ensures specific environment for a single test		Yes Spock contains four methods for setting up environments :setup() (run before every feature method), cleanup() (run after every feature method), setupSpec() (run before the first feature method), cleanupSpec() (run after the last feature method)
Group fixtures Allows defining a fixed, specific states of data for a group of tests (group-fixtures). This ensures specific environment for a given group of tests.	Yes Using the cucumber extension aruba you can create fixures in two steps: 1.Create a fixtures-directory; 2.Create fixture files in this directory	Yes You can use the fixture methods to setup environments for groups of tests.
Generators Supports data generators for tests. Data generators generate input data for test. The test is then run for each input data produced in this way.	Yes You can group your fixtures inside your fixtures directories	N/A
Licence Licence type governing the use and redistribution of the software	MIT License	Apache License 2.0
Mocks Mocks are objects that simulate the behavior of real objects. Using mocks allows testing some part of the code in isolation (with other parts mocked when needed)	Yes By using all of RSpec’s supported mocking frameworks (RSpec, Mocha, RR, Flexmock)	Yes Spock has inbuilt mocking capabilities and has no need for external libraries
Grouping Allows organizing tests in groups	Yes Cucumber allows the use of tag Cucumber feature files or individual tests to group tests. Then, you can pass a Cucumber tagged expression at test execution that specifies the tag (grouped) tests to run. https://www.toolsqa.com/cucumber/cucumber-tags/	Yes You can create suites manually in spock
Other Other useful information about the testing framework