Couple typo fixes

Converting-Add-ons-to-Plugins.md

@@ -80,17 +80,17 @@ siteConfig.AddMiddleware(func(next httpserver.Handler) httpserver.Handler {
 Instead of calling `setup.NewTestController()` like you did before, call `caddy.NewTestController()`:
 
 ```go
-c := caddy.NewTestController(input)
+c := caddy.NewTestController("http", input)
 ```
 
 To test that the middleware was set up properly, you'll need to get the config it was added to. The test controller uses an empty string key:
 
 ```go
-cfg := httpserver.GetConfig("")
+cfg := httpserver.GetConfig(c)
 mids := cfg.Middleware() // []httpserver.Middleware
 ```
 
-From there, you'll usually want the last middleware in the list, `mids[len(mids)-1]`. If you're not in a loop you can just assume `mids[0]`. Of course, if you didn't add any middleware, you can omit these checks.
+From there, you'll usually want the last middleware in the list, `mids[len(mids)-1]`. If you're not in a loop or you created a new controller each time, you can just assume `mids[0]`. Of course, if you didn't add any middleware, you can omit these checks.
 
 ## 4. Register plugin