Second time I’ve seen this, a self closing tag is one where the opening tag can close itself with a / dash, and doesn’t require an entirely new closing tag.
@bastien.virmaux You are correct, there is currently a bug in the test. HTML does not require a forward slash at the end of a self-closing tag but the FCC test does require it. So for the time being, make sure you always add a forward slash at the end (/>) of any self-closing tag to pass the FCC tests.