I've noticed that a lot of programmers see the value of testing on a rational level. If you've heard things like "yeah, I know I should test this but I really need to get this done quickly" then you know what I mean. However, on an emotional level they feel that they get something done only when they're writing the real code.
The goal, then, should be to somehow get them to understand that testing is in fact the only way to measure when something is "done", and thus give them the intrinsic motivation to write tests.
I'm afraid that's a lot harder than it should be, though. You'll hear a lot of excuses along the lines of "I'm in a real hurry, I'll rewrite/refactor this later and then add the tests" -- and of course, the followup never happens because, surprisingly, they're just as busy the next week.
