A recruiter approached me about the opening and then I was invited to their online test and was asked to build an API for a module of an application. The thing is, the requirements are very vague, I had to ask and clarify the requirements several times and the answers were always given more than a day after the questions were asked. Mind you I only had one week to finish the test. I ended up being rejected but didn't find out about it until I followed up to the recruiter.
The least they could do is notify me directly and give feedback, not just give arbitrary reason like "not up to their bar".