TestNG vs NUnit comparison of testing frameworks
What are the differences between TestNG and NUnit?

TestNG

https://testng.org/doc/documentation-main.html

NUnit

https://nunit.org/
Programming language

Java

.NET

Category

Unit Testing, Intergration Testing, End-to-End Testing

Unit Testing

General info

TestNG is a testing framework for the Java programming language inspired by JUnit and NUnit

TestNG is similar to JUnit and NUnit but with newer functionalities such as: annotations, test that your code is multithread safe, flexible test configuration, support for data-driven testing (with @DataProvider), support for parameters, powerful execution model (no more TestSuite) and more... It's also designed to cover all categories of tests unit, functional, end-to-end, intergration... etc

NUnit is an open-source unit testing framework for Microsoft .NET.

NUnit was Initially ported from JUnit. Tests can be run from a console runner, within Visual Studio through a Test Adapter or through 3rd party runners. Tests can be run in parallel and has Strong support for data driven tests. Unit supports multiple platforms including .NET Core, Xamarin Mobile, Compact Framework and Silverlight.
xUnit
Set of frameworks originating from SUnit (Smalltalk's testing framework). They share similar structure and functionality.

No

Yes

Nunit is one of many programs in the xUnit family
Client-side
Allows testing code execution on the client, such as a web browser

Yes

The scope of testing with testNg is wide and you can test various front-end functionalities and behaviours with it

Yes

You can test front-end components with NUnit since it is a Unit testing framework the application is isolated into diverse modules which are tested independently
Server-side
Allows testing the bahovior of a server-side code

Yes

You can test server-side functionalities and behaviours with TestNg

Yes

You can test back-end components with NUnit, it is a Unit testing framework hence the application is isolated into diverse modules which are tested independently
Fixtures
Allows defining a fixed, specific states of data (fixtures) that are test-local. This ensures specific environment for a single test

Yes

Fixtures are inbuilt into testNG, these are the annotations which are: @BeforeSuite, @AfterSuite, @BeforeTest, @AfterTest, @BeforeGroups, @AfterGroups, @BeforeClass, @AfterClass, @BeforeMethod, @AfterMethod

Yes

NUnit contains the fixture methods SetUp to initialize your test environment and TearDown method to destroy a test environment
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 various fixtures to setup environments for group tests

Yes

Group fixtures are available in NUnit
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

Apache License 2.0

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)

Yes

By Use of an external library like mockit which intergrates well with testNG

Yes

You can create mock objects using the third party library moq
Grouping
Allows organizing tests in groups

Yes

Multiple test cases can be grouped more easily by converting them into testng.xml file, in which you can make priorities which test case should be executed first

Yes

You can group tests into suites with NUnit
Other
Other useful information about the testing framework