How to make small templates and include them in a file?

Question

Pug

It is necessary that when adding to the main page it would be possible to dynamically change the
main file block:

doctype
html(lang='en')
    head
        meta(charset='utf-8')
        title
    body
        //Подключаем файл "test"

test file
h1 Сюда вставляем данные