Test for pull request #304 (Added try-catch to notification close in …

…symbol destructor) (#369)

* Added try-catch to notification close in symbol destructor

* Add test for try-catch to notification close in symbol destructor

* Update changelog

* More elegant way to test for error not raised.

Use self.fail() now instead of self.assert().
Thanks to @RobtertoRoos for pointing it out.

---------

Co-authored-by: Roberto-R <robert.soor@gmail.com>
Co-authored-by: chrisbeardy <20585410+chrisbeardy@users.noreply.github.com>

CHANGELOG.md

@@ -10,6 +10,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 * [#293](https://github.com/stlehmann/pyads/pull/2939) Support WSTRINGS in structures
 
 ### Changed
+* [#369](https://github.com/stlehmann/pyads/pull/304) Add test for [#304](https://github.com/stlehmann/pyads/pull/304) in `tests/test_testserver.py`
 * [#304](https://github.com/stlehmann/pyads/pull/304) Implemented try-catch when closing ADS notifications in AdsSymbol destructor
 * [#292](https://github.com/stlehmann/pyads/pull/292) Improve performance of get_value_from_ctype_data for arrays
 * [#363](https://github.com/stlehmann/pyads/pull/363) Allow for platform independent builds

tests/test_testserver.py

@@ -48,6 +48,42 @@ def test_context(self):
 
         time.sleep(0.1)  # Give server a moment to spin down
 
+    def test_server_disconnect_then_del_device_notification(self):
+        """Test no error thown, when ADS symbol with device_notification is cleaned up after the server went offline.
+
+        Tests fix of issue [#303](https://github.com/stlehmann/pyads/issues/303), original pull request: [#304](https://github.com/stlehmann/pyads/pull/304)
+        """
+        # 1. spin up the server
+        handler = BasicHandler()
+        test_server = AdsTestServer(handler=handler, logging=False)
+        test_server.start()
+        time.sleep(0.1)  # Give server a moment to spin up
+
+        # 2. open a plc connection to the test server:
+        plc = pyads.Connection(TEST_SERVER_AMS_NET_ID, TEST_SERVER_AMS_PORT)
+        plc.open()
+
+        # 3. add a variable, register a device notification with auto_update=True
+        test_int = pyads.AdsSymbol(plc, "TestSymbol", symbol_type=pyads.PLCTYPE_INT)
+        test_int.plc_type = pyads.PLCTYPE_INT
+        test_int.auto_update = True
+        time.sleep(0.1)  # Give server a moment
+
+        raised_error: str = ""
+
+        # 4. stop the test server
+        test_server.stop()
+        time.sleep(0.1)  # Give server a moment
+
+        try:
+            # some code, where test_int is cleared by the Garbage collector after the server was stopped
+            # (e.g. the machine with ADS Server disconnected)
+            # this raised an ADSError up to commit [a7af674](https://github.com/stlehmann/pyads/tree/a7af674b49b1c91966f2bac1f00f86273cbd9af8)
+            #  `clear_device_notifications()` failed, if not wrapped in try-catch as the server is no longer present.
+            test_int.__del__()
+        except pyads.ADSError as e:
+            self.fail(f"Closing server connection raised: {e}")
+
 
 if __name__ == "__main__":
     unittest.main()