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I'm trying to test my mac app under OSX El Capitan 10.11 and OSX Yosemite 10.10 , and am currently running macos Sierra 10.12. So far I've tried searching under the app store but none of the older version appear when searching. Also have tried checking the apple developer downloads section https://developer.apple.com/download/ , as well as the 'more downloads' section there.
Are there any options besides attempting to download a torrent of the older OS?