Unsupported test framework error in NUnit

It looks like you are trying to run NUnit3 tests with the NUnit2 Test Adapter. This is not supported.

You need to install the NUnit3 Test Adapter through Tools > Extensions and Updates in Visual Studio.

NUnit 3.x.y (NUnit 3.4.1) is compatible with NUnit3TestAdapter 3.x.y (NUnit3TestAdapter 3.4.0) NUnit 2.x.y (NUnit 2.6.4) is compatible with NUnitTestAdapter 2.x.y (NUnitTestAdapter 2.0.0)

If you use NUnit 3.x.y you have to install NUnit3TestAdapter 3.x.y instead of NUnitTestAdapter 2.x.y

I am using Microsoft Visual Studio Community 2015 and Microsoft .NET Framework 4.x

Steps to follow for installation:
1. Open Visual Studio and create a project
2. Right click on project -> Click on "Manage Nuget Packages..." from context menu
3. From pop up window: Install NUnit 3.x.y and NUnit3TestAdapter 3.x.y
4. Now run your tests

NUnit 3 only runs with NUnit test adapter 3 or latest version since there is compatibility issue with the older version 2.0. so if you have an exception like this:NUnit VS Adapter 2.0.0.0 discovering tests is started Attempt to load assembly with unsupported test framework in c:....... NUnit VS Adapter 2.0.0.0 discovering test is finished then all you need to do is to install the latest version of NUnit and NUnit test adapter on to your project be right clicking referencence on your solution explorer and manage Nuget packages.