testing-concept-reduction-in-cognitive-load means you will have a greater capacity (and willingness) to look for additional edge-cases in your code.
This is related to testing-concept-testing-forces-reflection, but in this case I don't think of it as forcing reflection, but by holding the context of what you've been working on, it allows reflection.
A critical component to this is testing-concept-push-variation-into-faster-tests, since it's only through those fast variations that you will be able to test edge cases without it becoming tedious.
Another thing that drives testing edge cases is the ease with which you can run the tests and get helpful results. testing-concept-do-not-to-leave-the-editor comes into play here.