Tests: added Python threading tests.

test/test_python_application.py

@@ -832,3 +832,44 @@ last line: 987654321
         assert 'success' in self.conf_delete('applications/callable/callable')
 
         assert self.get()['status'] == 204, 'default response 2'
+
+    def test_python_application_threads(self):
+        self.load('threads')
+
+        assert 'success' in self.conf(
+            '4', 'applications/threads/threads'
+        ), 'configure 4 threads'
+
+        socks = []
+
+        for i in range(4):
+            (_, sock) = self.get(
+                headers={
+                    'Host': 'localhost',
+                    'X-Delay': '2',
+                    'Connection': 'close',
+                },
+                no_recv=True,
+                start=True,
+            )
+
+            socks.append(sock)
+
+        threads = set()
+
+        for sock in socks:
+            resp = self.recvall(sock).decode('utf-8')
+
+            self.log_in(resp)
+
+            resp = self._resp_to_dict(resp)
+
+            assert resp['status'] == 200, 'status'
+
+            threads.add(resp['headers']['X-Thread'])
+
+            assert resp['headers']['Wsgi-Multithread'] == 'True', 'multithread'
+
+            sock.close()
+
+        assert len(socks) == len(threads), 'threads differs'