I've been building my first full blown ember app since the start of the year. I haven't got up to speed with testing yet (as opposed to my usual cucumber/rspec combo with ruby). I can tell you it is painful! I'm used to being able to change code on a whim, safe in the knowledge that my test suite is going to tell me about any regressions. We're using ember-data and there's some changes (like changing a model's association from sync to async) that can have consequences far from the code that you're working on so we've been seeing a lot of regressions. This has meant we're doing a huge amount of manual testing (I'm the only dev but there's 2 biz guys so this balance works at the moment). But I'll definitely be spending the rest of the week getting up to speed with ember testing. Maybe you can get away without tests if you have a really strong type system (i.e. better than java's) but for dynamic languages I think you're in for a world of pain without that safety net.