Spock vs Unit.js comparison of testing frameworks
What are the differences between Spock and Unit.js?

Spock

http://spockframework.org/

Unit.js

https://unitjs.com/
Programming language

Java

JavaScript

Category

Unit Testing

Unit Testing, End-to-End Testing

General info

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

An assertion library for JavaScript (similar to chai.js)

It works with any test runner and unit testing framework like Mocha, Jasmine, Karma, protractor (E2E test framework for Angular apps) and QUnit.
xUnit
Set of frameworks originating from SUnit (Smalltalk's testing framework). They share similar structure and functionality.

No

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

Yes

Spock tests front-end components and functionality by unit testing individual classes and functions

Yes

Unit.js runs in the browser to test front-end components
Server-side
Allows testing the bahovior of a server-side code

Yes

Spock tests back-end components and functionality by unit testing individual classes and functions

Yes

Unit.js runs in nodejs to test server-side behaviour
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)

Yes

Unit.js provides Test fixtures for running testsThis is one of its features
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

You can use the fixture methods to setup environments for groups of tests.

Yes

With Unit.js you can group your fixtures
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.

N/A

Licence
Licence type governing the use and redistribution of the software

Apache License 2.0

GNU

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

Spock has inbuilt mocking capabilities and has no need for external libraries

N/A

Grouping
Allows organizing tests in groups

Yes

You can create suites manually in spock

N/A

Other
Other useful information about the testing framework