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

Robot Framework

https://robotframework.org/

NUnit

https://nunit.org/
Programming language

Python

.NET

Category

Acceptance Testing

Unit Testing

General info

Robot is a Python framework used for acceptance/functional testing

Robot is an automated test framework which has a simple plain text syntax and can be extended easily with Python or Java libraries. It can run on the .net-based IronPython and on Jython which is Java based.

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

Robot has a rich library and can also be easily integrated with Selenium for browser automation to test front-end components

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

Robot can be used for back-end tests as well

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

There is no inbuilt way to work with fixtures in Robot however it can integrate with unittest and use fixtures that way

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.

By integrating with unittest

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.

Yes

Robot has a library called the Robot Framework Faker library. It contains 147 keywords used for generating random test data

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

Robot can access Python's mock library for mocking

Yes

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

Yes

One can create a test suite with Robot

Yes

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