How to make tests see pug (html) file?

Question

PhantomJS

There is a pug page that has a canvas. You need to write a test that checks if events work with this canvas. In the test, when I try to get the offsetWidth value of the canvas element, I get the error undefined is not an object (evaluating 'Board.offsetWidth'). As I understand it, this error means that the test does not know about the existence of the pug page. Where is it necessary to indicate the existence of this page? I tried to specify karmas in the files and preprocessors sections in the config, but this did not help. The technologies used are listed in the tags.