I have some open source projects that I've released on multiple occasions without having tested them. I think people make the assumption that things that have adequate documentation and comments/support tickets, etc. that indicate use, that they are tested before release. That is simply untrue. You get what you get. That is true in the world of both paid and unpaid open-source and closed-source software and well as life in-general.

Something that helps in this regard is travis-ci. It's a free CI server and if you have at least some level of testing, you have some level of confidence.