As someone who used to study software quality extensively, I really find it hard to agree with much of this article. The only form of testing that should be kept away from developers is end-user acceptance testing. There are plenty other forms of testing that /must/ be in the developers' hands.
"Developers tend to test the things they wrote the software to do". Agreed. But this is why you need to have well-written test plans (and automated testing) which offer as much coverage as possible. This /forces/ developers to test properly. This is also the reason for having end-users do end-user testing.
But what about other forms of testing?
Now you are obviously looking at this not just from a development perspective but also (I assume, with your position at ownCloud) from a commercial one. Well, I learned a thing or two at my time at +Kolab Systems
... Sure, we could always rely on the +Kolab.org Community
to do plenty testing for us... But Kolab Sys still had to do the bulk-load of it... Why? Because we were (and still do) release a /product/. Products come with expectations. Now this is very important in the case of ownCoud, just as it is with Kolab... You provide a warranty! Look at clause 4 here, if you do not believe me (https://owncloud.com/licenses/owncloud-commercial/
) :) If you are not doing thorough testing to a plan within the 4 walls of ownCloud Inc that warranty is going to end up costing you big-time in the long-run.
I'm glad to see that you have testing documentation... Excellent. However, please tell me that you have plenty evidence from inside the company that your own engineers are following these plans and producing reproducible results showing those tests passing. Because, if you're not, that warranty ain't worth much.