I have to agree that you would need to do the test in a lab but pre-testing can easily be done with a low cost spectrum analyzer and sniffer probes (1000 usd) and is a very useful tool to find the RF hot spots on your design. This can both help you pass the test in the first try and also llimit the costs later to find what is actually the problem if you fails.

Once you have the EMC-test report (passed or failed) you can easily find the same characteristics with the sniffer probe but the actual levels is not the same. But you can atleast clearly see if the changes you do to the product helps or not.

Also it is a great tool for production verification to make sure your products comply with the EMC after a while.