Github user NicoK commented on a diff in the pull request: https://github.com/apache/flink/pull/4533#discussion_r154321125 --- Diff: flink-runtime/src/test/java/org/apache/flink/runtime/io/network/netty/PartitionRequestClientHandlerTest.java --- @@ -244,54 +237,89 @@ public void testCancelBeforeActive() throws Exception { } /** - * Verifies that {@link RemoteInputChannel} is enqueued in the pipeline, and - * {@link AddCredit} message is sent to the producer. + * Verifies that {@link RemoteInputChannel} is enqueued in the pipeline for notifying credits, + * and verifies the behaviour of credit notification by triggering channel's writability changed. */ @Test public void testNotifyCreditAvailable() throws Exception { + final SingleInputGate inputGate = createSingleInputGate(); + final RemoteInputChannel inputChannel1 = spy(createRemoteInputChannel(inputGate)); + final RemoteInputChannel inputChannel2 = spy(createRemoteInputChannel(inputGate)); final CreditBasedClientHandler handler = new CreditBasedClientHandler(); - final EmbeddedChannel channel = new EmbeddedChannel(handler); + final EmbeddedChannel channel = spy(new EmbeddedChannel(handler)); - final RemoteInputChannel inputChannel = createRemoteInputChannel(mock(SingleInputGate.class)); + // Increase the credits to enqueue the input channels + inputChannel1.increaseCredit(1); + inputChannel2.increaseCredit(1); + handler.notifyCreditAvailable(inputChannel1); + handler.notifyCreditAvailable(inputChannel2); - // Enqueue the input channel - handler.notifyCreditAvailable(inputChannel); + channel.runPendingTasks(); + + // The two input channels should notify credits via writable channel + assertTrue(channel.isWritable()); + assertEquals(channel.readOutbound().getClass(), AddCredit.class); + verify(inputChannel1, times(1)).getAndResetCredit(); + verify(inputChannel2, times(1)).getAndResetCredit(); --- End diff -- Instead of verifying the method being called, we could add a (test-visible) `getUnannouncedCredit()` method and check the actual credit (since this new method would only read the state, it is ok to have it).
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