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

Unit.js

https://unitjs.com/

Spek

https://www.spekframework.org/
Programming language

JavaScript

Kotlin

Category

Unit Testing, End-to-End Testing

Acceptance Testing, Unit Testing

General info

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.

Spek is a specification framework for Kotlin

Spek is a Kotlin-based Specification Testing framework for the JVM. It works as a JUnit 5 Test Engine meaning that we can easily plug it into any project that already uses JUnit 5 to run alongside any other tests that we might have.
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

Unit.js runs in the browser to test front-end components

Yes

Yes you can test front-end behaviour by writing specifications to test front-end functionality. Developers can also write unit tests for individual front-end components.
Server-side
Allows testing the bahovior of a server-side code

Yes

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

Yes

You can test back-end behaviour and componets by writing specifications to test back-end functionality and unit tests for individual back-end components
Fixtures
Allows defining a fixed, specific states of data (fixtures) that are test-local. This ensures specific environment for a single test

Yes

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

Yes

Fixtures are available in spek through functions suchas beforeEachTest() and afterEachTest()
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

With Unit.js you can group your fixtures

Yes

spek has group fixtures available through the beforeGroup() and afterGroup() functions
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

GNU

Modified BSD License

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)

N/A

Yes

You can use the third party library mockito-kotlin
Grouping
Allows organizing tests in groups

N/A

Yes

Tests are written using nested lambdas, each scope (level) can either be a group or a test
Other
Other useful information about the testing framework