You might look into Extreme Programming; XP practioners would argue that the split between design and coding is rather arbitrary -- that much of the time spent in "coding" is actually spent thinking about design. And they would also say that 10% of time for actual testing would be too high, since you'd spend a lot of time up front making automated test suites (you build the test code first, and then design/code until the tests pass). Once you have all your testing automated, the actual time spent on testing is quite small. Of course, the time spent writing the test suites will be significant.