How to use the tox.venv.VirtualEnv function in tox

def create_test_env(config, mocksession, envname):

    venv = VirtualEnv(config.envconfigs[envname])
    action = mocksession.newaction(venv, "getenv")
    tox_testenv_create(action=action, venv=venv)
    pcalls = mocksession._pcalls
    assert len(pcalls) == 1
    pcalls[:] = []

    return venv, action, pcalls

def test_conda_create(newconfig, mocksession):
    config = newconfig(
        [],
        """
        [testenv:py123]
    """,
    )

    venv = VirtualEnv(config.envconfigs["py123"])
    assert venv.path == config.envconfigs["py123"].envdir

    action = mocksession.newaction(venv, "getenv")
    tox_testenv_create(action=action, venv=venv)
    pcalls = mocksession._pcalls
    assert len(pcalls) == 1
    assert "conda" in pcalls[0].args[0]
    assert "create" == pcalls[0].args[1]
    assert "--yes" == pcalls[0].args[2]
    assert "-p" == pcalls[0].args[3]
    assert venv.path == pcalls[0].args[4]
    assert pcalls[0].args[5].startswith("python=")

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

def tox_testenv_install_deps(self, action, venv):
            assert isinstance(action, tox.session.Action)
            assert isinstance(venv, VirtualEnv)
            log.append(2)

def _makevenv(self, name):
        envconfig = self.config.envconfigs.get(name, None)
        if envconfig is None:
            self.report.error("unknown environment {!r}".format(name))
            raise LookupError(name)
        elif envconfig.envdir == self.config.toxinidir:
            self.report.error(
                "venv {!r} in {} would delete project".format(name, envconfig.envdir)
            )
            raise tox.exception.ConfigError("envdir must not equal toxinidir")
        venv = VirtualEnv(envconfig=envconfig, session=self)
        self._name2venv[name] = venv
        return venv

def getvenv(self, name):
        if name in self.existing_venvs:
            return self.existing_venvs[name]
        env_config = self.config.envconfigs.get(name, None)
        if env_config is None:
            reporter.error("unknown environment {!r}".format(name))
            raise LookupError(name)
        elif env_config.envdir == self.config.toxinidir:
            reporter.error("venv {!r} in {} would delete project".format(name, env_config.envdir))
            raise tox.exception.ConfigError("envdir must not equal toxinidir")
        env_log = self.resultlog.get_envlog(name)
        venv = VirtualEnv(envconfig=env_config, popen=self.popen, env_log=env_log)
        self.existing_venvs[name] = venv
        return venv