I dare to make one last attempt to change your mind, before I would actually delete `CustomTimeoutTest` as you are suggesting:

* Without the test we would have missed some of the required changes (cf. conversations and original change suggestion by dsaff: "(3) [...] visibility of fields").
* Without this test the code in `CustomFailOnTimeout.createTimeoutException()` would not have been become like this: and somehow this does not look very nice to me yet or in other words smelly, so maybe the `FailOnTimeout` classes code with respect to timeout exception creation should be refactored too to allow for nicer re-use in `CustomFailOnTimeout`. Frankly I have not yet thought about the details or a concrete approach, but only the currently needed code in this test pointed out this kind of weakness? => should I try to elaborate in this direction?
* I personally think that tests are often the best type of documentation.