specifying fixture argument for py.test from command line

Question

I'd like to pass a command line argument to py.test for fixture creation. For example, I'd like to pass a database hostname to the fixture creation below, so it won't be hard-coded:

import pytest

def pytest_addoption(parser):
    parser.addoption("--hostname", action="store", default='127.0.0.1', help="specify IP of test host")

@pytest.fixture(scope='module')
def db(request):
    return 'CONNECTED TO [' + request.config.getoption('--hostname') + '] SUCCESSFULLY!'

def test_1(db):
    print db
    assert 0

Unfortunately, the default is not set, if the argument is omitted from the command line:

$ py.test test_opt.py
=================================================================== test session starts ====================================================================
platform linux2 -- Python 2.7.5 -- pytest-2.3.5
collected 1 items

test_opt.py E

========================================================================== ERRORS ==========================================================================
_________________________________________________________________ ERROR at setup of test_1 _________________________________________________________________

request = <FixtureRequest for <Module 'test_opt.py'>>

    @pytest.fixture(scope='module')
    def db(request):
>       return 'CONNECTED TO [' + request.config.getoption('--hostname') + '] SUCCESSFULLY!'

test_opt.py:8:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <_pytest.config.Config object at 0x220c4d0>, name = '--hostname'

    def getoption(self, name):
        """ return command line option value.

            :arg name: name of the option.  You may also specify
                the literal ``--OPT`` option instead of the "dest" option name.
            """
        name = self._opt2dest.get(name, name)
        try:
            return getattr(self.option, name)
        except AttributeError:
>           raise ValueError("no option named %r" % (name,))
E           ValueError: no option named '--hostname'

What am I missing? ... Incidentally, specifying the hostname on the command line also fails:

$ py.test --hostname=192.168.0.1 test_opt.py
Usage: py.test [options] [file_or_dir] [file_or_dir] [...]

py.test: error: no such option: --hostname

TIA!

Answer 1

What is the layout of your files? It seems you are trying to put all this code in the test_opt.py module. However the pytest_addoption() hook will only get read from a conftest.py file. So you should try moving the pytest_addoption() function to a conftest.py file in the same directory as test_opt.py.

In general while fixtures can be defined in test modules any hooks need to be placed in a conftest.py file for py.test to use them.