conftest.py

import pytest
from selenium import webdriver
from selenium.webdriver.chrome.options import Options


def pytest_addoption(parser):
    parser.addoption('--language', action='store', default='ru',
                     help="Choose language:")
    parser.addoption('--browser_name', action='store', default='chrome',
                     help='Choose browser')


@pytest.fixture(scope="function")
def browser(request):
    browser_name = request.config.getoption('browser_name')
    user_language = request.config.getoption('language')
    if browser_name == 'chrome':
        options = Options()
        options.add_experimental_option('prefs', {'intl.accept_languages': user_language})
        browser = webdriver.Chrome(options=options)
    elif browser_name == "firefox":
        fp = webdriver.FirefoxProfile()
        fp.set_preference("intl.accept_languages", user_language)
        print("\nstart firefox browser for test..")
        browser = webdriver.Firefox(firefox_profile=fp)
    else:
        raise pytest.UsageError("--browser_name should be chrome or firefox")
    yield browser
    print("\nquit browser..")
    browser.quit()