But then again, it may be easier to just set a single round goal like 100% for test coverage. Writing that test for the single expression setter won't cost you a lot.
Now, the correct response may well be to decide that that particular bit of code shouldn't be tested after all. Sometimes this means adding a /coverage skip if: an outgrabed momerath is hard to reproduce on demand/ for a particularly tricky corner case, but more often it means that you haven't correctly separated your concerns and that particular piece of code actually belongs in a file that's not touched by the test suite.
I doubt anyone does that. Having weird requirements like "all public methods should have at least one test" is insane. For many code bases that would be an order of magnitude more tests than a requirement of "100% test coverage"
Yeah, usually it won't cost anything to the guy who writes the test, but he is actually paid. What it costs to the business/customer/etc and whether the value added is worth of the cost is totally different matter.
I think there is clear incentive for writing unnecessary tests for certain developers - it is non-risky general work, where it is is difficult to fuck up anyway. If you are able to sell test-writing hours, what's the downside?
You can lose a business because of the heavy costs which add little value, however it is not easily arguable that a specific cost was the deal-breaker.