In my case, I offered to do it for free. (It wasn't their idea to give me a task on the actual codebase.) Almost nobody would be fine with that, but I want to w

In my case, I offered to do it for free. (It wasn't their idea to give me a task on the actual codebase.) Almost nobody would be fine with that, but I want to work there. The other option was to hope that none of the other candidates seemed like a better choice. It's good to lock in an opportunity. Perhaps it's unworkable in the general case. That would be unfortunate; it's the most effective type of interview.