import pytest
from selenium import webdriver

def pytest_addoption(parser):
    parser.addoption('--browser_name', action='store', default=None,
                     help="Choose browser: chrome or firefox")

link = "http://selenium1py.pythonanywhere.com/"

def test_guest_should_see_login_link(browser):
    browser.get(link)
    browser.find_element_by_css_selector("#login_link")

#pytest -s -v --browser_name=chrome test_parser.py
#pytest -s -v --browser_name=firefox test_parser.py