Problems with pytest's addoptions and dynamically parametrizing test fixtures

Question

I am using pytest to do software testing lately but am coming across a problem when dynamically parameterizing test fixtures. When testing, I would like to be able to provide the option to:

A) Test a specific file by specifying its file name

B) Test all files in the installed root directory

Below is my current conftest.py. What I want it to do is if you choose option A (--file_name), create a parameterized test fixture using the file name specified. If you choose option B (--all_files), provide a list of all the files as a parameterized test fixture.

import os
import pytest

def pytest_addoption(parser):
    parser.addoption("--file_name", action="store", default=[], help="Specify file-under-test")
    parser.addoption("--all_files", action="store_true", help="Option to test all files root directory")

@pytest.fixture(scope='module')
def file_name(request):
    return request.config.getoption('--file_name')

def pytest_generate_tests(metafunc):
    if 'file_name' in metafunc.fixturenames:
        if metafunc.config.option.all_files:
            all_files = list_all_files()
        else:
            all_files = "?"
        metafunc.parametrize("file_name", all_files)


def list_all_files():
    root_directory = '/opt/'
    if os.listdir(root_directory):
        # files have .cool extension that need to be split out
        return [name.split(".cool")[0] for name in os.listdir(root_directory)
                if os.path.isdir(os.path.join(root_directory, name))]
    else:
        print "No .cool files found in {}".format(root_directory)

The more I fiddle with this, I only can get one of the options working but not the other...what do I need to do to get both options (and possibly more) dynamically create parametrized test fixtures?

Answer 1

Are you looking for something like this?

def pytest_generate_tests(metafunc):
    if 'file_name' in metafunc.fixturenames:
        files = []
        if metafunc.config.option.all_files:
            files = list_all_files()
        fn = metafunc.config.option.file_name
        if fn:
            files.append(fn)
        metafunc.parametrize('file_name', all_files, scope='module')

No need to define file_name function.