gh-149141: Fix test discovery failure when srcpath contains symlink(s)

Lib/unittest/loader.py

@@ -356,7 +356,10 @@ def _get_name_from_path(self, path):
             return '.'
         path = _splitext(os.path.normpath(path))
 
-        _relpath = os.path.relpath(path, self._top_level_dir)
+        path_real = os.path.realpath(path)
+        tld_real = os.path.realpath(self._top_level_dir)
+        _relpath = os.path.relpath(path_real, tld_real)
+
         assert not os.path.isabs(_relpath), "Path must be within the project"
         assert not _relpath.startswith('..'), "Path must be within the project"
 

Misc/NEWS.d/next/Tests/2026-04-29-11-20-43.gh-issue-149141.Ue1Qww.rst

@@ -0,0 +1,4 @@
+Test discovery would fail when the path to the source tree contains a
+symlink. Paths that take an alternate route to the same place (eg just the
+real path) would not be considered a subpath, and cause an assert. Instead,
+always resolve to the real path before comparing.