Lens vs Jest comparison of testing frameworks
What are the differences between Lens and Jest?

Lens

https://github.com/spencer-mortensen/lens

Jest

https://jestjs.io
Programming language

PHP

JavaScript

Category

Unit Testing

Unit Testing

General info

Lens is a unit-testing framework for PHP

Lens is a unit-testing framework for PHP that needs no assertions

A Unit Testing framework focused on simplicity

This is a Unit test framwork especially designed for the React.JS, Babel, TypeScript, Node, React, Angular and Vue projects. It usually worked with Enzyme(Integration testing)
xUnit
Set of frameworks originating from SUnit (Smalltalk's testing framework). They share similar structure and functionality.

N/A

No

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

Yes

It can test front end components

Yes

You can easily test methods, properties, UI element actions and other front-end functionalities
Server-side
Allows testing the bahovior of a server-side code

Yes

It can test back-end behaviour

Yes

Back-end server behaviour also can be tested with Jest much in the same way as the front-end tests.
Fixtures
Allows defining a fixed, specific states of data (fixtures) that are test-local. This ensures specific environment for a single test

N/A

Yes

Fixtures are supported, Jest has many helper functions such as: BeforeEach and afterEach If you have some work you need to do repeatedly for many tests, beforeAll and afterAll if you only need to do setup once, at the beginning of a file.
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.

N/A

Yes

Jest supports group 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

N/A

Licence
Licence type governing the use and redistribution of the software

N/A

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

Jest uses a custom resolver for imports in your tests making it simple to mock any object outside of your test’s scope. You can use mocked imports with the rich Mock Functions API to spy on function calls with readable test syntax.
Grouping
Allows organizing tests in groups

N/A

Yes

You can declare as many test suites as you want. Grouping of tests together is done using a describe block
Other
Other useful information about the testing framework