This testing point is spot on. Last night, I was getting killed with little bugs on some dynamic menu / tab widget where things got added and deleted and the active tab needed to move around smartly. Knockout allowed me to whip up 30 tests for the expected behavior and then make sure my view model worked correctly and had a decent API before turning to the actual view. With just a few commands I could bind this to the view and all the functionality worked flawlessly.