Test builds of Zotero (also known as ‘dev’-channel builds) are intended for one-off testing of specific non-public changes that haven't yet been rolled out to a beta build or release build. Test builds are not regularly updated and may not be stable, and you should use them only when a Zotero developer asks you to test a specific change. Do not use a test build for production work.
Once you've finished testing the change in question, you should return to a release or beta build.