gh-116738: Make _suggestions module thread-safe (gh-140321)

Lib/test/test_free_threading/test_suggestions.py

@@ -0,0 +1,24 @@
+import unittest
+
+from test.support import import_helper, threading_helper
+from test.support.threading_helper import run_concurrently
+
+suggestions = import_helper.import_module("_suggestions")
+
+NTHREADS = 10
+
+
+@threading_helper.requires_working_threading()
+class SuggestionsTests(unittest.TestCase):
+    def test_generate_suggestions(self):
+        candidates = [str(i) for i in range(100)]
+
+        def worker():
+            _ = suggestions._generate_suggestions(candidates, "42")
+            candidates.clear()
+
+        run_concurrently(worker_func=worker, nthreads=NTHREADS)
+
+
+if __name__ == "__main__":
+    unittest.main()