How much time do they usually give you to do this?

I tried, I think the problem with this website. I will wait and try again.

But how can I know that I need to write that expression (I mean $x("//input[@testid = 'field_username']") in console tab, if I don't know that xpath yet?

Alex, can you please explain how to find xpath? I wrote in 'console' $x("//input[@testid = 'field_username']") but I actually don't understand what to do with the result. I also tried on another examples where we use it and I still don't get it.