How is the training system at Codecademy arranged?

Question

HTML

I decided to start developing a learning system for html, I decided to take Codecademy as a prototype (according to the plan, the system should work in c++).
I tried to find it on the Internet but to no avail, so I decided to turn to you for help.
I will be glad to any answer.

Answer 1

There is nothing fundamentally and conceptually different from the classical systems of sports programming or testing in CodeAcademy.
We sent a solution, interpreted / compiled a piece of code, ran it through the tests, got the result. Html - document markup language, already easier.
How to check html for correctness. Well, probably check the presence of tags with the given parameters, i.e. parse the DOM, somehow compare with a sample.
Such considerations

Answer 2

apparently the tag "machine learning" is superfluous here