Spending a week working beside an engineer (or seeing how they complete a substantial project) almost certainly provides a better measure of their abilities than watching them solve interview problems for 1 hour Trial employment is expensive for the company. [...] Trial employment (and large take-home projects) are expensive for the candidate. I can't help but think there's way to mitigate that expense among several…
That's an interesting idea! The hard part would be convincing companies to trust an external trial week fully (part of what's great about a trial week is the chance to actually see how an engineer will interact with your team / your problems). But I like the idea!
Surely a company could objectively learn a great deal about a candidate by looking at a week's worth of git commits and evaluating the final product for correctness/maintainability/optimization.
But still, taking TOO much of the humanity out of hiring ignores the fact that ultimately, a person has to work with other people, so you're right that it's not perfect.