The server factory could not be located for the given input: Microsoft.Owin.Host.HttpListener
Solution 1:
The Microsoft.Owin.Host.HttpListener assembly is a runtime reference in WebApp.Start. You need to include it in the project's references for it to be available for loading. Check the bin\Debug (etc) directory to make sure it's included. May as well add it as a nuget dependency as well.
Solution 2:
Install the package:
PM> Install-Package Microsoft.Owin.Host.HttpListener