@pytest.hookimpl()
    def pytest_addoption(parser):
    """Creates a parser option"""

    # Allows the user to select the test suite they want to run
    parser.addoption("--suite", action="store", default="None"
                     , choices=['a', 'b']
                     , help="Choose which test suite to run.")

    @pytest.hookimpl()
    def pytest_configure(config):
        print("Determining test directory")
        suite = config.getoption("--suite")

            if suite == "a":
                config.addinivalue_line("testpaths", "tests/a")

            elif suite == "b":
                config.addinivalue_line("testpaths", "tests/b")