[inventitech]

The first step is just to observe how much time is spent on testing. We have basically no clue about this. And our first study with students has also shown that they had no clue about it.

In a second step, we can think about which implication testing time might have on quality. As you said correctly, more time does not necessarily correlate with better quality or higher productiveness. Maybe there is a certain range of testing efforts that can be associated with good quality tests? E.g. if you spend less than x on testing, your tests are likely to be bad. If you spend more than y on testing, it might be worth investigating whether you have unusually high testing targets. Or your tests might be extremely hard to maintain.

I think the answer is Janus-faced and there is no single, simple answer (see also "Testivus on Test Coverage", http://www.artima.com/weblogs/viewpost.jsp?thread=204677).