Test what the domain fact would change to

domain_test.rb

require 'win32ole'
require 'win32/registry'

def connect(uri = wmi_resource_uri)
  WIN32OLE.connect(uri)
end

def wmi_resource_uri( host = '.' )
  "winmgmts:{impersonationLevel=impersonate}!//#{host}/root/cimv2"
end

def execquery(query)
  connect().execquery(query)
end

def hklm_read(key, value)
  Win32::Registry::HKEY_LOCAL_MACHINE.open(key) {|reg| reg[value]}
end

primary = hklm_read('SYSTEM\CurrentControlSet\Services\Tcpip\Parameters', 'Domain')
puts "primary  : #{primary}"

dnsdomain = ""
execquery("select DNSDomain from Win32_NetworkAdapterConfiguration where IPEnabled = True").each { |nic|
  dnsdomain = nic.DNSDomain
  break
}
puts "interface: #{dnsdomain}"

if primary.empty? or primary == dnsdomain
  puts "domain would not change"
else
  puts "domain would change from '#{dnsdomain}' to '#{primary}'"
end