For a test suite I have, each test has a failure rate (from 0 to 1), where 1 means it fails every time and 0 means it never fails, and a duration in ms (this is unbounded). I want a metric (I think either multiplication or division) that will capture the knowledge that tests with a low duration have a high value, and tests that have a high failure rate have a high value.
What is the appropriate metric for this?