Tests: harden TestNetwork even more

- test task.stop()
- use more lenient timeout
- make sure we always collect two frames

test/test_network.py

@@ -57,6 +57,7 @@ def test_send_periodic(self):
         DATA2 = bytes([4, 5, 6])
         COB_ID = 0x123
         PERIOD = 0.1
+        TIMEOUT = PERIOD * 10
         self.network.connect(
             interface="virtual",
             channel=1,
@@ -68,27 +69,40 @@ def test_send_periodic(self):
         event = Event()
 
         def hook(_, data, ts):
-            acc.append((data, ts))
-            event.set()
+            if len(acc) < 2:
+                acc.append((data, ts))
+            else:
+                event.set()
 
         self.network.subscribe(COB_ID, hook)
         self.addCleanup(self.network.unsubscribe, COB_ID)
 
+        def check(expected):
+            data = [v[0] for v in acc]
+            self.assertEqual(data, [expected] * 2)
+            ts = [v[1] for v in acc]
+            delta = (ts[-1] - ts[0]) / (len(ts) - 1)
+            self.assertAlmostEqual(delta, PERIOD, places=1)
+
         task = self.network.send_periodic(COB_ID, DATA1, PERIOD)
         self.addCleanup(task.stop)
 
-        event.wait(PERIOD*2)
+        # Wait for two frames to arrive; then check the result.
+        event.wait(TIMEOUT)
+        check(DATA1)
 
-        # Update task data.
+        # Update task data, which implicitly restarts the timer.
         task.update(DATA2)
+        acc.clear()
         event.clear()
-        event.wait(PERIOD*2)
-        task.stop()
 
-        data = [v[0] for v in acc]
-        self.assertEqual(data, [DATA1, DATA2])
-        ts = [v[1] for v in acc]
-        self.assertAlmostEqual(ts[1]-ts[0], PERIOD, places=1)
+        # Wait for two frames to arrive; then check the result.
+        event.wait(TIMEOUT)
+        check(DATA2)
+
+        # Stop the task.
+        task.stop()
+        self.assertIsNone(self.network.bus.recv(TIMEOUT))
 
 
 class TestScanner(unittest.TestCase):