Yes, you can.
When testing on a local, non-public site, you can even activate the add-on without it counting towards the activation limit. Make sure that you simply need to run your plugin on a URL that matches to one of these properties:
If you are running the plugin on one of those URLs then the activation works even if you hit your limit.
You can always manage your activations in your account. In case our license system cannot determine your site as non-public, you can just deactivate the license on your test environment to use it on your live site after testing. There should be a button for this behind the activated license key. You can also send us the URLs of your test sites if they are not detected automatically and we will add it to your license.
If you need multiple activated licenses then please check out the large discounts we offer for larger volumes of license keys.