Add test capturing missed expectation. Ref #117.

Author: jaraco

importlib_metadata/tests/test_zip.py

@@ -1,7 +1,10 @@
 import sys
 import unittest
 
-from .. import distribution, entry_points, files, PackageNotFoundError, version
+from .. import (
+    distribution, entry_points, files, PackageNotFoundError,
+    version, distributions,
+    )
 
 try:
     from importlib.resources import path
@@ -52,6 +55,10 @@ def test_files(self):
             path = str(file.dist.locate_file(file))
             assert '.whl/' in path, path
 
+    def test_one_distribution(self):
+        dists = list(distributions(path=sys.path[:1]))
+        assert len(dists) == 1
+
 
 class TestEgg(TestZip):
     def setUp(self):