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

RSpec

https://rspec.info

Spock

http://spockframework.org/
Programming language

Ruby

Java

Category

Unit Testing, Intergration Testing

Unit Testing

General info

Domain Specific Language (DSL) testing solution for Ruby code

It focuses on empowering Test Driven Development (TDD). RSpec contains multiple smaller libraries, which may be independently used with other testing frameworks.

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.

Yes

Yes, but it differs from more traiditional xUnit solutions. Its tests are written in a "Tests as Specification" manner. This means that the terminology used in RSpec is adjusted to a language more fitting for specification.

No

Client-side
Allows testing code execution on the client, such as a web browser

Yes

RSpec is used to primarily test the behaviour of applications or individual components so it can test front-end behaviour as well - you can use capybara gem with RSpec for that.

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 server-side behaviour with Rspec

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

RSpec does contain fixture methods

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

Group fixture methods are supported

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

RSpec contains generators for example intergration_'test_name' which will save a spec inside the spec/requests folder

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

Available through rspec-mocks gem.

Yes

Spock has inbuilt mocking capabilities and has no need for external libraries
Grouping
Allows organizing tests in groups

Yes

Allows declaring example groups and contexts.

Yes

You can create suites manually in spock
Other
Other useful information about the testing framework