What work tests/type of application questions have you found most valuable in finding the right candidates/filtering out good fits?
And if you do work trials, how valuable have you found them ?
We do work tests for all roles, operations or not. I think they are far and away the most valuable part of our hiring process.
The ones I have found the most useful for operations hiring:
Having people to work through hypothetical complicated financial problems like sending a candidate a list of rules for how transactions should be entered into a spreadsheet, then giving them a list of sample transaction with tons of mistakes and asking them to correct the mistakes, and then giving a list of new entries and seeing if they do it correctly.
Asking someone how the would resolve a hypothetical complicated situation involving HR compliance, financial compliance, etc. all bundled together.
The least helpful:
Asking people to write something (especially if the role involves communications) - folks interviewing often just don’t seem to know your organization well enough to communicate about it well prior to working at the org., and it’s really hard to compare these against each other besides on the basis of grammar, etc.
In a (written) work test I would usually try to have a situation that is similar to something slightly challenging that would be encountered in the actual work (Something that is based on an actual situation but adjusted so that it works well for a test environment is usually good.). This allows to get at least some idea on how people would address a problem at work in practice and I would try to incorporate to test for some of these skills:
General problem-solving capability (by making the task open enough to allow for some creativity)
Ability to follow instructions (by giving clear instructions on what needs to be done including relevant details)
Ability to structure thoughts and organise things (by asking eg to create a high-level timeline for some event planning or other activity)
Attention to detail (by a) potential documents the candidate creates and b) including bits in the tasks that get easily missed without a strong attention to detail)
(Written) communication skills (by asking eg to write a reply to an email as part of the task)
What exactly you would do would of course depend on the specific characteristics of the role (eg if the role involves a strong Finance component you would probably add something specifically relevant to that eg dealing with spreadsheets).
For these kind of generalist skills, a work test in my experience works relatively well in separating very good from merely ‘okay’ candidates (And usually quite easily identifies bad candidates.)
There are other skills that are very well tested in interviews or similar situations and the combination of a work test and an interview has in my experience worked to judge candidates for (junior) ops roles.