diff --git a/test/lib/helper.py b/test/lib/helper.py
@@ -10,6 +10,8 @@
import logging
import os
import os.path as osp
import tempfile
import textwrap
import time
@@ -411,6 +413,13 @@ def __init__(self, env_dir, *, with_pip):
            self._env_dir = env_dir
            venv.create(self.env_dir, symlinks=True, with_pip=with_pip)

    @property
    def env_dir(self):
        """The top-level directory of the environment."""