We are still at a point where minor changes can result in dozens of "change detected" triggers, of which we are not sure how to determine whether they represent corrections or regressions (it's usually not at all obvious.)
I've also been weary of building a large "accuracy testing suite" for the SNES, on the fear that if I come to the wrong conclusion on something, others will emulate that inaccuracy and won't question it because of deference to my code.
Tests also have the unfortunate side-effect of being gamified (example: http://tasvideos.org/EmulatorResources/NESAccuracyTests.html), which is a very bad thing. Failing a test because we don't know the answer is infinitely better than passing the test using am unverified guess. But when people reduce a comprehensive and complex set of tests into a percentage score, you get a very skewed picture of what actually matters. (think of how browsers jumped through hoops to pass the Acid CSS tests back in the day.)
It is however something that's important, and hopefully I'll have the time one day to work on this more.