I was recently interviewing for a new job. One company asked me to solve a coding challenge. I had one free evening to do it and managed to get it mostly done but didn't feel comfortable submitting it as there was still a few issues and I didn't have time to clean it up like I wanted to.

The other company asked for some code samples of work I had already done and then I walked them through it to show that I understood it and what design decisions and trade-offs I had made and why.

The company that asked for code samples ended up making me an offer and due to lack of time and the fact that another company was already interested in hiring me, I never even continued the conversation with the coding challenge company.

It seems that if a coding challenge is trivial then it doesn't really prove much. There's probably an answer for something close to it online and even if the candidate did solve it on their own it's still too trivial.

If a coding challenge is complex enough to actually test a candidates range of knowledge then it's often not worth it to complete the challenge for a possible job opportunity.