title: ASP.NET infrastructure in MediatR handlers
body: <p>I prefer to keep my handlers free from ASP.NET infrastructure that is very hard to test (yes, even in ASP.NET Core). But sometimes it happens and you have a dependency like UserManager (I'd like to know one day why it's not an interface), HttpContext, etc. and unit-tests are turned into a mocking-hell.</p>
  
  <p>I tried using integration testing to deal with it by creating a TestServer and having all the ASP.NET infrastructure initialized for every api call. It works quite well but sometimes seems like an overkill if I want to  test simple logic of my handler. And while it solves technical problem of mocking ASP.NET infrastructure, it keeps architectural problem (if you consider it so) of having ASP.NET infrastructure into your handlers.</p>
  
  <p>I'd like to know what are the recommended approaches to deal with it?</p>