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

Behat

https://docs.behat.org/en/latest/

RSpec

https://rspec.info
Programming language

PHP

Ruby

Category

Functional/Acceptance Testing

Unit Testing, Intergration Testing

General info

Behat is an open source Behavior-Driven Development framework for PHP.

Behat uses the StoryBDD subtype of behaviour-driven development (the other subtype is SpecBDD); This means the tests we write with Behat look rather like stories than code. It is inspired by Ruby's Cucumber

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.
xUnit
Set of frameworks originating from SUnit (Smalltalk's testing framework). They share similar structure and functionality.

No

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

Yes

To enable Behat to test a website, you need to add Mink and a browser emulator (selenium maybe, though slow) to the mix. Mink methods are the connector between Behat and an extensive list of available drivers, and they provide a consistent testing API.

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.
Server-side
Allows testing the bahovior of a server-side code

Yes

Behat can be used for Data Integrity Testing to verify that database operations are functioning properly

Yes

You can test server-side behaviour with Rspec
Fixtures
Allows defining a fixed, specific states of data (fixtures) that are test-local. This ensures specific environment for a single test

Yes

One can use the 'Doctrinefixturesbundle' to create the required fixture loaders and load them in our Behat scenarios when required, using the 'BeforeScenario' hook.

Yes

RSpec does contain fixture methods
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

Behat allows for group fixtures

Yes

Group fixture methods are supported
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.

By use of third party libraries like moodle-behat-generators

Yes

RSpec contains generators for example intergration_'test_name' which will save a spec inside the spec/requests folder
Licence
Licence type governing the use and redistribution of the software

MIT License

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)

By using third party libraries like Mock and Prophecy

Yes

Available through rspec-mocks gem.
Grouping
Allows organizing tests in groups

Yes

You can use tags to group features and scenarios together, independent of your file and directory structure

Yes

Allows declaring example groups and contexts.
Other
Other useful information about the testing framework