Tests must be maintained, and that means they must be revisited. Reviewability is how easy it is to come back to a test and understand it. Test programs are easily added to suites. In some suites I've seen, it's major surgery just to add a new test. Make it easy and the suite will grow more quickly.
Tests are rapidly accessible.
I once saw a test management system where it took more than 30 seconds to navigate to a single test from the top level of the system. It discouraged test review and test development. Design the system such that you can access a given test in no more than a few seconds. Also, make sure the tests are accessible by anyone on the team. Tests are traceable to a test outline.