I'm new to Concordion and just started trying it out.
I downloaded their example "Kickstart" project at https://github.com/concordion/concordion-net-kickstart/releases/tag/v1.2.0 and I also created my own project to get a better sense of how it works.
When I attempt to run my tests in both the Kickstart project and my own project that I created I encounter the same errors:
NUnit VS Adapter 2.0.0.0 discovering tests is started Exception System.NullReferenceException, Exception thrown discovering tests in C:\Users......\concordion-net-kickstart-1.2.0\Kickstart.Spec\bin\Debug\Kickstart.Spec.dll NUnit VS Adapter 2.0.0.0 discovering test is finished
I'm not sure why this is happening or what's causing this as I ran their example project straight out of the box and even then it was tossing back the same exception as my own project that I created.
Congratulation for your first Concordion.NET tests.
Unfortunately, there is an issue with the NUnit Test Adapter (https://github.com/nunit/nunit-vs-adapter/issues/9) that prevents loading of NUnit addins such as the one used to run Concordion.NET tests.
As described on the website of Concordion, there is a workaround to be able to run Concordion.NET tests with the NUnit Test Adapter: http://concordion.org/dotnet/RunningTests.html#test-adapter
You can use another NUnit client to run Concordion.NET tests:
I hope you enjoy Concordion.NET. Please, don't hesitate to ask any further questions.