Ask HN: What's a Good Coding Test?

I've been asked to create a coding test to assess candidates during the hiring process.

I have mixed feelings about coding tests; they increase the entry barrier and put the company at risk of losing the busiest persons (who may otherwise be very good).

My own experience has also been mixed. Sometimes the test is poorly written and thus speaks badly about the company (why should I put the effort in taking a test when the person who wrote it didn't take the time to fix the grammar and the requirements?). Sometimes they feel exploitative (write a simple app for candidates to upload resumes to our company, write a case study over the tools you would use to create our new data analysis platform).

Also, don't get me started about the algorithm test you find on many online services.

I also don't like when I'm asked to take a coding test before talking with the company at least once.

Still, a well-written coding test may speak well about the company and could be positive in getting the tech interview started.

What's a good coding test you'd feel like doing? And what other advice can you give me about that, besides the raw coding challenge?

In case you ask, I'm looking for a good developer with a good attitude regarding team play (this is probably not testable with a coding test, but it felt worth saying).

Thank you in advance for any suggestions! :)