When I start seeing actual numbers from an Interactive Designer, such as what % of users can solve their test cases. Then we'll become great friends!

See that? Right there. The whole "It must have a number target that we can obsess-compulse about!"
That's the 50 foot marshmallow man talking.
Trying to put numbers on human competence is hard. Does mildly annoying count as half a virtually unusable, or a third?
Not to mention that the whole point of interactive design is to make sure that the user doesn't have to "solve" anything.

Guidelines of Select New Furniture
The following are basic guidelines to help you select new furniture pieces:

Finish—Look for a consistent finish, color, and grain in wood surfaces as well as being smooth to the touch. Ask the retailer what the finish will stand up to. Will it endure heat and water spills? It should. Poorer quality furniture may be stained to camouflage imperfections in wood color or grain, whereas a better piece is more likely to have a clear finish that enables you to see the grain of the wood.

Dressers, Chests, and Nightstands—Make sure that the drawers in these pieces feel substantial, slide easily with drawer stops, and fit evenly without gaps or misalignment. If you see staples or nails, this is most likely a sign of lesser quality. Higher-end pieces have solid wood drawer sides and dove-tailed joints as well as dust panels between each drawer.

Structure—Don't be afraid to ask about the construction of the piece of furniture you like. Most wood furniture is built using "floating construction," which means that it allows for expansion and contraction of wood panels in dry or humid weather throughout the seasons. If you pick up the piece, you shouldn't hear a lot of noise due to racking because the frame should be solid. Where the sides and top come together, make sure that it's a tightly assembled with no gaps or glue visible. The back of the piece shouldn't bulge or be out of square, nor should there be unevenness or poor fit in any of the other areas of the piece.

If you know what to look for, you can get better quality furniture for less money. By shopping around and broadening your options, you can find plenty of places like antique stores, wood furniture store, and thrift stores, for instance, www.fuzi-wood-furniture.com, that have good stuff at lower prices. The key to getting your money's worth is shopping carefully to meet your decorating goals. Sometimes it's better to get a a really superior piece, especially if you love it, than settle for a lower quality piece. And sometimes getting a practical, mid-range piece is exactly right for your needs. Once you recognize value, you'll be able to shop wisely and create the dcor of your dreams.

Ok, folks, let's talk about metaphor and hyperbole, shall we?

"Metaphor (n.) - a figure of speech in which a term or phrase is applied to something to which it is not literally applicable in order to suggest a resemblance."

"Hyperbole (n.) - an extravagant statement or figure of speech not intended to be taken literally, as 'to wait an eternity.'" (Both definitions are from Dictionary.com.)

Jeff is applying both constructs to this post.

His metaphor is that a user choosing not to use an application is a kind of unit test. If users pass over an application because it's UI design is terrible, that's a unit test failure. Essentially, users "unit test," too, but they do so by not using our applications.

His hyperbole is that this form of unit testing trumps all other forms of unit testing. That is, if we can't get users to even USE our applications, then all our other unit tests are inconsequential. This is hyperbole because it's obviously not true. Read through some of Jeff's other posts you'll see that he's a unit testing proponent.

The other point that Jeff makes is that we engineers like to ENGINEER (and by implication we don't like that mushy UI design stuff) and we're a controlling lot. If we ARE actually unit testing, we engineers like to make sure that we get good test coverage, that we've tested everything the best that we can. However, there's one unit test we tend not to cover and that's making sure our UI design makes user WANT to use our apps. Obsessing over unit testing and test coverage when our users won't use our applications is a waste of time (more hyperbole).

I hope this brings some clarity to the posts about how unit testing and UI design aren't related. They aren't, much. But that's not the point Jeff's is trying to make. He's telling us that usability is more important than almost everything else -- maybe even unit testing.