Make the assertion explicit.

importlib_resources/tests/test_path.py

@@ -1,4 +1,5 @@
 import io
+import pathlib
 import unittest
 
 import importlib_resources as resources
@@ -15,13 +16,11 @@ def execute(self, package, path):
 class PathTests:
     def test_reading(self):
         """
-        Path should be readable.
-
-        Test also implicitly verifies the returned object is a pathlib.Path
-        instance.
+        Path should be readable and a pathlib.Path instance.
         """
         target = resources.files(self.data) / 'utf-8.file'
         with resources.as_file(target) as path:
+            self.assertIsInstance(path, pathlib.Path)
             self.assertTrue(path.name.endswith("utf-8.file"), repr(path))
             self.assertEqual('Hello, UTF-8 world!\n', path.read_text(encoding='utf-8'))