request = <SubRequest 'app' for <Function test_add_group[None:;;]>>

    @pytest.fixture
    def app(request):
        global fixture
        if fixture is None:
            browser = request.config.getoption("--browser")
>           fixture = Application(browser=browser)

conftest.py:13:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <fixture.application.Application object at 0x0324BA50>, browser = 'firefox'

    def __init__(self, browser="Firefox"):
        if browser == "Firefox":
            self.wd = webdriver.Firefox()
        elif browser == "Chrome":
            self.wd = webdriver.Chrome()
        elif browser == "Ie":
            self.wd = webdriver.Ie()
        else:
>           raise ValueError("Unrecognized browser %s" % browser)
E           ValueError: Unrecognized browser firefox

fixture\application.py:17: ValueError