bpo-40094: Enhance threading tests (GH-19260)

* Rewrite test_thread.test_forkinthread() to use
  support.wait_process() and wait for the child process in the main
  thread, not in the spawned thread.
* test_threading now uses support.wait_process() and checks the child
  process exit code to detect crashes.

1 files changed, 19 insertions, 18 deletions

diff --git a/Lib/test/test_thread.py b/Lib/test/test_thread.py
index 9f4801f..77e46f2 100644
--- a/Lib/test/test_thread.py
+++ b/Lib/test/test_thread.py
@@ -225,30 +225,31 @@ class TestForkInThread(unittest.TestCase):
     @unittest.skipUnless(hasattr(os, 'fork'), 'need os.fork')
     @support.reap_threads
     def test_forkinthread(self):
-        status = "not set"
+        pid = None
 
-        def thread1():
-            nonlocal status
+        def fork_thread(read_fd, write_fd):
+            nonlocal pid
 
             # fork in a thread
             pid = os.fork()
-            if pid == 0:
-                # child
-                try:
-                    os.close(self.read_fd)
-                    os.write(self.write_fd, b"OK")
-                finally:
-                    os._exit(0)
-            else:
-                # parent
-                os.close(self.write_fd)
-                pid, status = os.waitpid(pid, 0)
+            if pid:
+                # parent process
+                return
+
+            # child process
+            try:
+                os.close(read_fd)
+                os.write(write_fd, b"OK")
+            finally:
+                os._exit(0)
 
         with support.wait_threads_exit():
-            thread.start_new_thread(thread1, ())
-            self.assertEqual(os.read(self.read_fd, 2), b"OK",
-                             "Unable to fork() in thread")
-        self.assertEqual(status, 0)
+            thread.start_new_thread(fork_thread, (self.read_fd, self.write_fd))
+            self.assertEqual(os.read(self.read_fd, 2), b"OK")
+            os.close(self.write_fd)
+
+        self.assertIsNotNone(pid)
+        support.wait_process(pid, exitcode=0)
 
     def tearDown(self):
         try: