As of this writing, Akka.TestUnit.NUnit and NUnit 3 are incompatible with one another. Specifically, package version 1.0.5 and NUnit 3.0.1. I’ve opened an issue with the Akka.net team (Issue 1651) so you can watch it for the resolution to this problem.
I was trying to test Akka.net actors in a project that was already using NUnit 3.x. I wrote the tests, but when I ran them with the ReSharper test runner, they would show up for just a split-second and then disappear. I thought that maybe it was the ReSharper test runner since that very day I had to upgrade from R# 9 to R# 10 to get the NUnit 3 support. I tried running the tests from the NUnit 3 console runner and experienced the same thing, though. The tests weren’t failing or marked ignored, or even “not run”, the test runner just didn’t pick them up at all. With a little help from the good folks at the Akka.net Gitter chat, I was able to get my tests running by downgrading to NUnit 2.6. I suppose it is a “known” issue but maybe not that well known since there was no issue logged for it 🙂