"Simple feature test on the front page"
Not a major WTF by any standard, but it seems the "simple feature test on the main page" worked...since its still there on the live site.
I admit I have done this to a site I am being paid to manage, but it only took 3-4 days for me to notice and it has a very low traffic (the site has frequent users, but they don't tend to go to the front page), so I got away with it. Also,my boss was out bush for a fortnight, so he wasn't able to see the site and notice my mistake, and since he has the technical abilities of a concussed gnat, he wouldn't have done anything anyway.
This just means that the slightly more complicated feature test to follow the first one failed. (That being to delete the test post.)
This sort of thing is perfectly reasonable for any developer to do if they have no test environment, and their hardware only has a couple of ports on it. (One for file transfers, the other for HTTP.) Oh, and it doesn't have a GUI console, so they can't view it from a localhost-only instance, and they only have the one ID. I'm probably forgetting one or two limitations, such as the OS lacking the ability to redirect to a different web server based on the incoming IP.