You basically have 3 options, depending on what you really want to do.
- Test whether a page correctly shows the content it`s supposed to
Selenium's webdriver.get($URL) waits for the page to load completely, as in the "cancel loading" button in your browser changes to "refresh". Otherwise you could implicitly wait (https://www.seleniumhq.org/docs/04_webdriver_advanced.jsp) for all the elements you want loaded. Then you can take a screenshot / test the page.
- Test whether a page contains all the elements you want
A better option would be to use a webscraping library to GET the particular page and check whether it contains specified elements and text. This will be much faster than Selenium. However, there is no GUI and you might run into some problems with parsing.
- Check that the page returns correct status code
In this case, I`d use something like Postman or Python requests library (or a HTTP library for a language of your choice). Send a GET request to the page and check that it returns the status code you want.