The testing of iOS 9.1 started before Apple even released the final version of iOS 9. Because now the same is happening with OS X.
Although it has not yet released the final version of OS X El Capitan 10.11 so far only developers and participants of the Apple Beta Software Program are testing the version Golden Master his (that is, the candidate for final) the tests of OS X El Capitan 10.11.1 started today.
Interested developers can download the 15B17c build right now by Apple Developer. According to Apple, the first update to El Capitan improves the stability, compatibility and security of the system. No areas have been highlighted for developers to focus their tests on.
Update · 09/17/2015 s 15:18
Like iOS 9.1 beta, OS X 10.11.1 beta also supports a huge range of new Emojis including tacos, burritos, cheese, hot dogs, unicorn heads and the polemic middle finger.
Update II, by Rafael Fischmann · 09/21/2015 s 18:05
And today, a few days later, Apple has now made the first test version of OS X 10.11.1 available to members of the Apple Beta Software Program. Whoever is part of it will already see the update automatically through the Mac App Store.