D3 js - Title tooltip not working

Hi all^^
I was trying to submit the bar-chart project but there’s something wrong; i was almost reporting it as a bug, but i feel github being so ‘official’…
That’s why i’m asking here if i’m not aware of something or if it’s really a bug to report.
Here is the link to the pen: link

Here the screenshot of the error and the behaviour on Chrome

It only works in Chrome so I can’t test it properly.

Ok, got it. The problem is here:

My chart should have a title with a corresponding id=“title”

I used the corresponding SVG title element, which in Chrome is displayed as tooltip but is not valid for the test.
I’m changing the title, maybe in the future someone will fall into the same misunderstanding^^
Thanks all anyway,