Comment by lucb1e | Hacker News Reader

Comment by lucb1e | Hacker News Reader

That's interesting, I've never heard testing code skills by reading instead of writing.

An example would have been nice though, as I'm not sure how to find a piece of code that does something standalone that is too large to grasp in 20 minutes yet make a reasonable prediction at the output. That combination seems kind of weird.

I wonder how well it would work to modify OP's idea and present a candidate with some code that has a bug in it (you reveal what the bug is to save time, they'll need to understand the code anyhow) and you ask them how they'd fix it. First broadly, like what approach, then actually write part of it.

To take my own advice and make the discussion more concrete, I should add an example. Random script from my github: https://github.com/lucb1e/randomdirectory/blob/master/random...

To prepare for the interview, one could add an argument like -h to show usage (in the same style as -v is currently implemented), then tell the candidate that the bug is that passing -vh executes neither -v nor -h (one would commonly expect it to execute both). Fixing this requires a 'structural' change to this little bit of code, but it's small enough to easily grasp and implement. The candidate might propose to loop over each character after a single hyphen to fix this, or they might propose to throw out this custom reinventing-the-wheel and use a proper arg parsing library. Either is fine, but they should be prepared to write the code (in any language, they can write just the changes in C, Python, JS, or whatever language they're comfortable with).

Has anyone tried such an interview coding question?

We used to have an interview process that had a take-home project.

The project was:

- you have two files: listings.json and products.json

- listings.json lists ~20,000 Amazon listings for electronics with fields like title, brand and price

- products.json lists ~1,000 digital cameras, with fields like brand, family, model

- your job is to write a script that, for each entry in listings.json, emits the best match (or no match!) from products.json

Your solution could be as naive or as fancy as you wanted. The main point was to have something for the next stage.

We'd run your submission, and use that to show you some false positives and false negatives. Then we'd ask you to debug why each false positive or false negative happen, explain it to us, propose how you'd fix it, and identify any trade-offs in your proposed fix.

Eventually, we wanted to offer a non-take-home-project interview. We already had a bunch of existing solutions from employees, so we used those to run a stripped down version of the interview that just focused on the code reading/debugging/proposing fixes part.

I think both of these interview approaches were pretty effective at giving candidates a natural environment to demonstrate skills that they'd actually use on the job -- debugging, collaboration, predicting downstream implications of changes, etc.

That's a great example that fits almost 1:1 with something we've been doing. I will propose that to avoid having to give take-home projects, thanks for sharing!

My favorite front end interview did this exact thing. The interview started with an issue taken straight from the Preact GitHub codebase. The interviewer provided the issue text and the commit right before it was fixed to pull down onto my machine. I had an hour to figure out how to build and reproduce the issue, Take in the high level structure of the code base, figure out how to drill down in a debugger to find where the issue itself was occurring, then propose a fix for it. Took the whole hour but was both extremely satisfying for me, and I imagine very insightful for the interviewer.

Preact maintainer here.

That's amazing! I didn't know that our little project is used in interviews. Happy to hear that you liked working with the code base!

This sounds fun

My company has an initiative to bring in students for a 3 day event where they attend workshops and talks.

We were brainstorming what type of content would make fun and educational workshops for students. I proposed something along OPs lines. I called them "debugging minichallenges". The idea is to present students with a buggy implementation for a simple problem, and they need to find and fix the bugs. Just as OPs argues, the concept is that reading and understanding code is a fundamental skill.

I have the set of sample implementations in my Github, for example the one in Python [1]. This is our first time running this workshop so I can report how well it did after the event.

[1] https://github.com/angarg12/minichallenge-flood-fill-python

Took a quick look and was not impressed to find a pycache[1] in your repo (unless that's one of the bugs the candidate was expected to find :-P )

[1] https://github.com/angarg12/minichallenge-flood-fill-python/...

Good idea. I'm not sure I know arg parsing libraries in every language though. Even so, hopefully talking about where to make the change and finding some good documentation on an arg parsing library would be good enough start for 20 minutes.

> I'm not sure I know arg parsing libraries in every language though.

In my opinion, you should be free to look that up: that's what you'd do on the job as well. I also google it every time I need to use arg parsing in literally any language because I need it fairly infrequently, and frankly that's how this code came to be: too lazy to look it up again, too easy to write myself, and enjoying the writing of code. Any other solution would also be fine, this test would be about seeing if you can read and write code rather than if you come up with the (what the interviewers think) is the perfect solution.

Yeah, we sometimes say stuff like "we don't expect you to know the arguments to sigaction just like that, you can ask us anything[1] or just put what you think could be reasonable", to make clear we're not looking to hire an encyclopedia.

[1] And if they do, we probably end up pulling up the man page for them because we don't remember either. It's just not the relevant part of any coding interview, the reading or the writing kind.

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