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I don't think that you actually have to test it, if this is on a website that you manage. Just make sure that the plugin is uploaded there, and you're done, and there will be no error.
If you want to make it available for people to download, then just add info in the README file that they have to upload the plugin, similar to how it was done in the TdmStats module. If people don't do it and then complain, you can point to the Readme file and the info there.
Am I missing something?