diff --git a/src/isolated_environment/__init__.py b/src/isolated_environment/__init__.py
index e5e9404..f72bc46 100644
--- a/src/isolated_environment/__init__.py
+++ b/src/isolated_environment/__init__.py
@@ -1,6 +1,6 @@
 from pathlib import Path
 from subprocess import CompletedProcess
-from typing import Any
+from typing import Any, Union
 
 from .api import IsolatedEnvironment  # noqa: F401
 from .requirements import Requirements  # noqa: F401
@@ -9,9 +9,11 @@
 
 
 def isolated_environment(
-    env_path: Path, requirements: list[str] | None = None
+    env_path: Union[Path, str], requirements: list[str] | None = None
 ) -> dict[str, Any]:
     """Creates an isolated environment."""
+    if isinstance(env_path, str):
+        env_path = Path(env_path)  # type: ignore
     requirements = requirements or []
     reqs = Requirements(requirements)
     iso_env = IsolatedEnvironment(env_path, reqs)
@@ -20,11 +22,13 @@ def isolated_environment(
 
 
 def isolated_environment_cmd(
-    env_path: Path,
+    env_path: Union[Path, str],
     cmd_list: list[str],
     requirements: list[str] | None,
 ) -> CompletedProcess:
     """Creates an isolated environment."""
+    if isinstance(env_path, str):
+        env_path = Path(env_path)  # type: ignore
     requirements = requirements or []
     reqs = Requirements(requirements)
     iso_env = IsolatedEnvironment(env_path, reqs)
diff --git a/tests/run.py b/tests/run.py
new file mode 100644
index 0000000..9905989
--- /dev/null
+++ b/tests/run.py
@@ -0,0 +1,11 @@
+import sys
+
+
+def main() -> int:
+    """Main function."""
+    print("Hello World!")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/tests/test_run_py_file.py b/tests/test_run_py_file.py
new file mode 100644
index 0000000..ebb6e8f
--- /dev/null
+++ b/tests/test_run_py_file.py
@@ -0,0 +1,50 @@
+"""
+Unit test file.
+"""
+
+import subprocess
+import unittest
+from pathlib import Path
+from tempfile import TemporaryDirectory
+
+from isolated_environment import isolated_environment
+
+HERE = Path(__file__).parent
+
+RUN_PY = HERE / "run.py"
+
+
+class MainTester(unittest.TestCase):
+    """Main tester class."""
+
+    def test_shell(self) -> None:
+        """Test command line interface (CLI)."""
+        with TemporaryDirectory() as tmp_dir:
+            venv_path = Path(tmp_dir) / "venv"
+            env = isolated_environment(venv_path, [])
+            cmd_list = [
+                "python",
+                str(RUN_PY),
+            ]
+            stdout: str = subprocess.check_output(
+                cmd_list, env=env, shell=True, universal_newlines=True
+            )
+            self.assertEqual("Hello World!\n", stdout)
+
+    def test_no_shell(self) -> None:
+        """Test command line interface (CLI)."""
+        with TemporaryDirectory() as tmp_dir:
+            venv_path = Path(tmp_dir) / "venv"
+            env = isolated_environment(venv_path, [])
+            cmd_list = [
+                "python",
+                str(RUN_PY),
+            ]
+            stdout: str = subprocess.check_output(
+                cmd_list, env=env, shell=False, universal_newlines=True
+            )
+            self.assertEqual("Hello World!\n", stdout)
+
+
+if __name__ == "__main__":
+    unittest.main()