I love writing automated tests, but having someone else test your own code is just different, I as the owner of the code will usually have a “positive” attitude

I love writing automated tests, but having someone else test your own code is just different, I as the owner of the code will usually have a “positive” attitude to my own code, this in my opinion limits my imagination towards all the things that can go wrong (TDD sometimes helps me but it has its limits). On the other hand, a QA tester has a “negative” attitude, he or she knows that there are bugs in the code and his/her work is to find them.