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

JUnit

https://junit.org/junit5/

Cucumber

https://github.com/cucumber/cucumber-ruby
Programming language

Java

Ruby

Category

Unit Testing, Regression Testing

Acceptance 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

An automation tool for Behavior-Driven Development

The specifications are written in plain texts, which allows them to be easily understandable for all stakeholders. Cucumber Framework also supports languages beyond Ruby e.g. Java, JavaScript and Scala.
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.

No

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

You can test the front-end part like the GUI using cucumber and selenium, they integrate well to test your front-end.
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 back-end components such as APIs using rest & soap clients, and databases using whatever client libraries were provided by the libraries that existed in those stacks
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.

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

Using the cucumber extension aruba you can create fixures in two steps: 1.Create a fixtures-directory; 2.Create fixture files in this directory
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

You can group your fixtures inside your fixtures directories
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

By using all of RSpec’s supported mocking frameworks (RSpec, Mocha, RR, Flexmock)
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.

No

Other
Other useful information about the testing framework