When it comes to test automation, I use a very arbitrary method based on experience that 80% of all tests should be automated.
This has worked well in practice, but is based more on "voodo" than science.
Should I instead be performing a mini return on investment analysis for each test to work out which ones I are good automation candidates?
Should I just focus on the buggiest areas of the application?
What is the best practiceare some good method(s) to determine when a test should be automated or not?
Is there a simple criteria that can be applied, or is it truly a black art?