How to use the tox.session function in tox

def test_subcommand_test_post_hook(self, mocker):
        """It should return the same retcode, but run the hook."""
        subcommand_test = mocker.patch('tox.session.Session.subcommand_test',
                                       return_value=42)
        tox_subcommand_test_post = mocker.Mock()
        subcommand_test_monkeypatch(tox_subcommand_test_post)

        import tox.session
        session = mocker.Mock()

        real_subcommand_test = tox.session.Session.subcommand_test
        # Python 2 compat
        real_subcommand_test = getattr(
            real_subcommand_test, '__func__', real_subcommand_test)

        assert real_subcommand_test(session) == 42
        subcommand_test.assert_called_once_with(session)
        tox_subcommand_test_post.assert_called_once_with(session.config)

def _collect_session(result):
        prev_build = tox.session.build_session

        def build_session(config):
            result.session = prev_build(config)
            return result.session

        monkeypatch.setattr(tox.session, "build_session", build_session)

def create_new_config_file_(args, source=None, plugins=(), filename="tox.ini"):
        if source is None:
            source = args
            args = []
        s = textwrap.dedent(source)
        p = tmpdir.join(filename)
        p.write(s)
        tox.session.setup_reporter(args)
        with tmpdir.as_cwd():
            return parseconfig(args, plugins=plugins)

def _collect_session(result):
        prev_build = tox.session.build_session

        def build_session(config):
            result.session = prev_build(config)
            return result.session

        monkeypatch.setattr(tox.session, "build_session", build_session)

def tox_testenv_create(self, action, venv):
            assert isinstance(action, tox.session.Action)
            assert isinstance(venv, VirtualEnv)
            log.append(1)

def run(self):
                prev_build = tox.session.build_session

                def build_session(config):
                    res.session = prev_build(config)
                    res._popen = res.session.popen
                    monkeypatch.setattr(res.session, "popen", popen)
                    return res.session

                monkeypatch.setattr(tox.session, "build_session", build_session)

                def popen(cmd, **kwargs):
                    activity_id = _actions[-1].name
                    activity_name = _actions[-1].activity
                    ret = "NOTSET"
                    try:
                        ret = res._popen(cmd, **kwargs)
                    except tox.exception.InvocationError as exception:
                        ret = exception
                    finally:
                        res.popens.append(
                            (activity_id, activity_name, kwargs.get("env"), ret, cmd)
                        )
                    return ret

                _actions = []

def test_provision_cli_args_ignore(cmd, initproj, monkeypatch, plugin):
    import tox.config
    import tox.session

    prev_ensure = tox.config.ParseIni.ensure_requires_satisfied

    @staticmethod
    def ensure_requires_satisfied(config, requires, min_version):
        result = prev_ensure(config, requires, min_version)
        config.run_provision = True
        return result

    monkeypatch.setattr(
        tox.config.ParseIni, "ensure_requires_satisfied", ensure_requires_satisfied
    )
    prev_get_venv = tox.session.Session.getvenv

    def getvenv(self, name):
        venv = prev_get_venv(self, name)
        venv.envconfig.envdir = py.path.local(sys.executable).dirpath().dirpath()
        venv.setupenv = lambda: True
        venv.finishvenv = lambda: True
        return venv

    monkeypatch.setattr(tox.session.Session, "getvenv", getvenv)
    initproj("test-0.1", {"tox.ini": "[tox]"})
    result = cmd("-a", "--option", "b")
    result.assert_success(is_run_test_env=False)

def prepare_tox(self):
        toxini = os.path.join(os.path.dirname(__file__), 'tox.ini')
        config = tox.session.prepare(['-c', toxini])
        name = uuid.uuid4().hex
        envconfig = TestenvConfig(name, config, None, None)
        envconfig.envdir = local('%s/%s' % (config.toxworkdir, name))
        envconfig.envlogdir = local('%s/log-%s' % (config.toxworkdir, name))
        envconfig.basepython = sys.executable
        envconfig.sitepackages = False
        envconfig.downloadcache = False
        envconfig.pip_pre = False
        envconfig.setenv = []
        envconfig.install_command = 'pip install {opts} {packages}'.split()
        config.envconfigs[name] = envconfig

        session = tox.session.Session(config)
        self.venv = session.getvenv(name)

def prepare_tox(self):
        toxini = os.path.join(os.path.dirname(__file__), 'tox.ini')
        config = tox.session.prepare(['-c', toxini])
        name = uuid.uuid4().hex
        envconfig = TestenvConfig(name, config, None, None)
        envconfig.envdir = local('%s/%s' % (config.toxworkdir, name))
        envconfig.envlogdir = local('%s/log-%s' % (config.toxworkdir, name))
        envconfig.basepython = sys.executable
        envconfig.sitepackages = False
        envconfig.downloadcache = False
        envconfig.pip_pre = False
        envconfig.setenv = []
        envconfig.install_command = 'pip install {opts} {packages}'.split()
        config.envconfigs[name] = envconfig

        session = tox.session.Session(config)
        self.venv = session.getvenv(name)

class FakeTerminalWriter(object):
    '''
    Redirect TerminalWriter messages to a log file
    '''
    hasmarkup = True

    def sep(self, char, message, **kwargs):
        return '-'

    def line(self, msg, *args, **kargs):
        retox_log.info("tox: " + msg)


class RetoxReporter(tox.session.Reporter):
    '''
    A custom tox reporter designed for updating a live UI
    '''

    screen = None
    env_frames = None

    def __init__(self, session):
        '''
        Create a new reporter

        :param session: The Tox Session
        :type  session: :class:`tox.session.Session`
        '''
        super(RetoxReporter, self).__init__(session)
        self._actionmayfinish = set()