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

JUnit

https://junit.org/junit5/

RSpec

https://rspec.info
Programming language

Java

Ruby

Category

Unit Testing, Regression Testing

Unit Testing, Intergration Testing

General info

JUnit is an open source Unit testing framework for java

JUnit is useful for developers to write and run repeatable tests. JUnit has been crucial in the development of test driven development and is partof the xUnit family of unit testing frameworks

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.

Yes

It is an instance of the xUnit architecture for unit testing frameworks.

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

You can test front-end components such as individual classes and functions that create the front-end

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

You can test classes and functions that compose the back-end such as database connections and so on

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

JUnit contains a setUp() method, which runs before every test invocation and a tearDown() method, which runs after every test method.

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

You can use setUp() and tearDown() inbuilt functions as 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.

You can use JUnit-quickcheck to generate test data

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

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)

JUnit does not support mocking internally but you can use a mock framework like Mockito to generate mock objects.

Yes

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

Yes

In JUnit you can create a test suite that bundles a few unit test cases and runs them together. You use both @RunWith and @Suite annotation are used to run the suite test.

Yes

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