A year or so ago, one of our devs got some questions on our test replaced with things of the type the maintenance team occasionally gets asked, instead of making it solely about development and bugfixing, though twisted a bit to be feasible in an interview test (for example, the source data they'd work on was something like a 3 MB JSON file instead of a database).
Questions involved figuring out how to manipulate that data, and since not a single one could be done solely with a library call it said a lot about their ability to think through a problem, as well as their knowledge of things like data structures and efficiency. The latter questions even built off of the earlier ones, as if the stakeholder came back with more questions.
With a reasonable knowledge of the language you were using, those questions would only take around 15-30 minutes total, and each answer (as long as you did correctly build on the previous ones) was only ~5-10 lines of code.
"Here is the almost complete skeleton of a project in your preferred language (presumably, the one you're applying to use full time), finish it by implementing this vital piece of business logic."
