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

Unit.js

https://unitjs.com/

NaturalSpec

https://www.nuget.org/packages/NaturalSpec/
Programming language

JavaScript

.NET

Category

Unit Testing, End-to-End 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.

NaturalSpec is a .NET Unit testing framework

NaturalSpec is a .NET UnitTest framework which provides automatically testable specs in natural language. NaturalSpec is based on NUnit and completely written in F# - you don't have to learn F# to use it.
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

You can test front-end components with NaturalSpecit. It is a Unit testing framework therefore you can test front-end modules and classes independently
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 components with NaturalSpec. It is a Unit testing framework therefore you can test back-end modules and classes independently
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

N/A

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

N/A

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

MIT 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

Mocks are available through third party libraries like Moq
Grouping
Allows organizing tests in groups

N/A

N/A

Other
Other useful information about the testing framework