Be careful with absolute statements. If you haven't tested it, how do you know it doesn't work? I'd say you know that no more than they know that it does, and the hyperbole doesn't help them understand. It just sounds like you're willing to either exaggerate (which you are) or to ignore the simple rules of logic (in which case testing wouldn't do any good anyway).
I think the best way to get around all this "sort of meets spec" thinking and to get people to do tests misses the obvious part of the problem. If you really want the software tested and you really want it to meet specs, then there's a solution staring you in the face. Spec the tests.
If you specify what the tests are, and specify that the software must meet the tests, then the software isn't fit for spec until it passes the tests. You may be a test first person, a test last person, a write then test per feature person, or whatever type of test-minded person you care to be. If the spec is written in terms of what tests specifically must pass and how the tests will be written, then there's no way to claim the software is to spec until the tests pass.
