Cannot set application pool for site in IIS via appcmd

I'm trying to set the application pool for a site via appcmd.

1. I add a pool:

   appcmd add apppool /name:"TestAppPool" /managedPipelineMode:Classic
   

2. I add a site:

   appcmd add site /name:"MyTestSite" /physicalPath:C:\MyTestSite
   

3. Then I set a pool for this site:

   appcmd set site /site.name:"MyTestSite" /[path='C:\MyTestSite'].applicationPool:TestAppPool
   

   Here I get an error:

   ERROR ( message:Cannot find requested collection element. )

What's wrong here?

Got it working with this:

appcmd add site /name:"MyTestSite" /bindings:"http/*:81:" /physicalPath:c:\MyTestSite

appcmd set site /site.name:"MyTestSite" /[path='/'].applicationPool:TestAppPool