added MqttTransportHandlerTest

+/**
+ * Copyright © 2016-2021 The Thingsboard Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.thingsboard.server.transport.mqtt;
+
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.EmptyByteBuf;
+import io.netty.buffer.PooledByteBufAllocator;
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.handler.codec.mqtt.MqttConnectMessage;
+import io.netty.handler.codec.mqtt.MqttConnectPayload;
+import io.netty.handler.codec.mqtt.MqttConnectVariableHeader;
+import io.netty.handler.codec.mqtt.MqttFixedHeader;
+import io.netty.handler.codec.mqtt.MqttMessage;
+import io.netty.handler.codec.mqtt.MqttMessageType;
+import io.netty.handler.codec.mqtt.MqttPublishMessage;
+import io.netty.handler.codec.mqtt.MqttPublishVariableHeader;
+import io.netty.handler.codec.mqtt.MqttQoS;
+import io.netty.handler.ssl.SslHandler;
+import lombok.extern.slf4j.Slf4j;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.junit.MockitoJUnitRunner;
+import org.thingsboard.common.util.ThingsBoardThreadFactory;
+
+import java.net.InetSocketAddress;
+import java.nio.charset.StandardCharsets;
+import java.util.List;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.contains;
+import static org.hamcrest.Matchers.empty;
+import static org.hamcrest.Matchers.greaterThan;
+import static org.hamcrest.Matchers.is;
+import static org.junit.Assert.fail;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.BDDMockito.willDoNothing;
+import static org.mockito.BDDMockito.willReturn;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+
+@Slf4j
+@RunWith(MockitoJUnitRunner.class)
+public class MqttTransportHandlerTest {
+
+    public static final int MSG_QUEUE_LIMIT = 10;
+    public static final InetSocketAddress IP_ADDR = new InetSocketAddress("127.0.0.1", 9876);
+    public static final int TIMEOUT = 30;
+
+    @Mock
+    MqttTransportContext context;
+    @Mock
+    SslHandler sslHandler;
+    @Mock
+    ChannelHandlerContext ctx;
+
+    AtomicInteger packedId = new AtomicInteger();
+    ExecutorService executor;
+    MqttTransportHandler handler;
+
+    @Before
+    public void setUp() throws Exception {
+        willReturn(MSG_QUEUE_LIMIT).given(context).getMessageQueueSizePerDeviceLimit();
+
+        handler = spy(new MqttTransportHandler(context, sslHandler));
+        willReturn(IP_ADDR).given(handler).getAddress(any());
+    }
+
+    @After
+    public void tearDown() {
+        if (executor != null) {
+            executor.shutdownNow();
+        }
+    }
+
+    @Test
+    public void givenMessageWithoutFixedHeader_whenProcessMqttMsg_thenProcessDisconnect() {
+        MqttFixedHeader mqttFixedHeader = null;
+        MqttMessage msg = new MqttMessage(mqttFixedHeader);
+        willDoNothing().given(handler).processDisconnect(ctx);
+
+        handler.processMqttMsg(ctx, msg);
+
+        assertThat(handler.address, is(IP_ADDR));
+        verify(handler, times(1)).processDisconnect(ctx);
+    }
+
+    MqttConnectMessage getMqttConnectMessage() {
+        MqttFixedHeader mqttFixedHeader = new MqttFixedHeader(MqttMessageType.CONNECT, true, MqttQoS.AT_LEAST_ONCE, false, 123);
+        MqttConnectVariableHeader variableHeader = new MqttConnectVariableHeader("device", packedId.incrementAndGet(), true, true, true, 1, true, false, 60);
+        MqttConnectPayload payload = new MqttConnectPayload("clientId", "topic", "message".getBytes(StandardCharsets.UTF_8), "username", "password".getBytes(StandardCharsets.UTF_8));
+        return new MqttConnectMessage(mqttFixedHeader, variableHeader, payload);
+    }
+
+    MqttPublishMessage getMqttPublishMessage() {
+        MqttFixedHeader mqttFixedHeader = new MqttFixedHeader(MqttMessageType.PUBLISH, true, MqttQoS.AT_LEAST_ONCE, false, 123);
+        MqttPublishVariableHeader variableHeader = new MqttPublishVariableHeader("v1/gateway/telemetry", packedId.incrementAndGet());
+        ByteBuf payload = new EmptyByteBuf(new PooledByteBufAllocator());
+        return new MqttPublishMessage(mqttFixedHeader, variableHeader, payload);
+    }
+
+    @Test
+    public void givenMqttConnectMessage_whenProcessMqttMsg_thenProcessConnect() {
+        MqttConnectMessage msg = getMqttConnectMessage();
+        willDoNothing().given(handler).processConnect(ctx, msg);
+
+        handler.processMqttMsg(ctx, msg);
+
+        assertThat(handler.address, is(IP_ADDR));
+        assertThat(handler.deviceSessionCtx.getChannel(), is(ctx));
+        verify(handler, never()).processDisconnect(any());
+        verify(handler, times(1)).processConnect(ctx, msg);
+    }
+
+    @Test
+    public void givenQueueLimit_whenEnqueueRegularSessionMsgOverLimit_thenOK() {
+        List<MqttPublishMessage> messages = Stream.generate(this::getMqttPublishMessage).limit(MSG_QUEUE_LIMIT).collect(Collectors.toList());
+        messages.forEach(msg -> handler.enqueueRegularSessionMsg(ctx, msg));
+        assertThat(handler.deviceSessionCtx.getMsgQueueSize().get(), is(MSG_QUEUE_LIMIT));
+        assertThat(handler.deviceSessionCtx.getMsgQueue(), contains(messages.toArray()));
+    }
+
+    @Test
+    public void givenQueueLimit_whenEnqueueRegularSessionMsgOverLimit_thenCtxClose() {
+        final int limit = MSG_QUEUE_LIMIT + 1;
+        willDoNothing().given(handler).processMsgQueue(ctx);
+        List<MqttPublishMessage> messages = Stream.generate(this::getMqttPublishMessage).limit(limit).collect(Collectors.toList());
+
+        messages.forEach((msg) -> handler.enqueueRegularSessionMsg(ctx, msg));
+
+        assertThat(handler.deviceSessionCtx.getMsgQueueSize().get(), is(limit));
+        verify(handler, times(limit)).enqueueRegularSessionMsg(any(), any());
+        verify(handler, times(MSG_QUEUE_LIMIT)).processMsgQueue(any());
+        verify(ctx, times(1)).close();
+    }
+
+    @Test
+    public void givenMqttConnectMessageAndPublishImmediately_whenProcessMqttMsg_thenEnqueueRegularSessionMsg() {
+        givenMqttConnectMessage_whenProcessMqttMsg_thenProcessConnect();
+
+        List<MqttPublishMessage> messages = Stream.generate(this::getMqttPublishMessage).limit(MSG_QUEUE_LIMIT).collect(Collectors.toList());
+
+        messages.forEach((msg) -> handler.processMqttMsg(ctx, msg));
+
+        assertThat(handler.address, is(IP_ADDR));
+        assertThat(handler.deviceSessionCtx.getChannel(), is(ctx));
+        assertThat(handler.deviceSessionCtx.getMsgQueueSize().get(), is(MSG_QUEUE_LIMIT));
+        assertThat(handler.deviceSessionCtx.getMsgQueue(), contains(messages.toArray()));
+        verify(handler, never()).processDisconnect(any());
+        verify(handler, times(1)).processConnect(any(), any());
+        verify(handler, times(MSG_QUEUE_LIMIT)).enqueueRegularSessionMsg(any(), any());
+        messages.forEach((msg) -> verify(handler, times(1)).enqueueRegularSessionMsg(ctx, msg));
+    }
+
+    @Test
+    public void givenMessageQueue_whenProcessMqttMsg_thenEnqueueRegularSessionMsg() throws InterruptedException {
+        //given
+        assertThat(handler.deviceSessionCtx.isConnected(), is(false));
+        assertThat(MSG_QUEUE_LIMIT, greaterThan(2));
+        List<MqttPublishMessage> messages = Stream.generate(this::getMqttPublishMessage).limit(MSG_QUEUE_LIMIT).collect(Collectors.toList());
+        messages.forEach((msg) -> handler.enqueueRegularSessionMsg(ctx, msg));
+        willDoNothing().given(handler).processRegularSessionMsg(any(), any());
+        executor = Executors.newCachedThreadPool(ThingsBoardThreadFactory.forName(getClass().getName()));
+
+        CountDownLatch readyLatch = new CountDownLatch(MSG_QUEUE_LIMIT);
+        CountDownLatch startLatch = new CountDownLatch(1);
+        CountDownLatch finishLatch = new CountDownLatch(MSG_QUEUE_LIMIT);
+
+        Stream.iterate(0, i -> i + 1).limit(MSG_QUEUE_LIMIT).forEach(x ->
+                executor.submit(() -> {
+                    try {
+                        readyLatch.countDown();
+                        assertThat(startLatch.await(TIMEOUT, TimeUnit.SECONDS), is(true));
+                        handler.processMsgQueue(ctx);
+                        finishLatch.countDown();
+                    } catch (Exception e) {
+                        log.error("Failed to run processMsgQueue", e);
+                        fail("Failed to run processMsgQueue");
+                    }
+                }));
+
+        //when
+        assertThat(readyLatch.await(TIMEOUT, TimeUnit.SECONDS), is(true));
+        handler.deviceSessionCtx.setConnected(true);
+        startLatch.countDown();
+        assertThat(finishLatch.await(TIMEOUT, TimeUnit.SECONDS), is(true));
+
+        //then
+        assertThat(handler.deviceSessionCtx.getMsgQueueSize().get(), is(0));
+        assertThat(handler.deviceSessionCtx.getMsgQueue(), empty());
+        verify(handler, times(MSG_QUEUE_LIMIT)).processRegularSessionMsg(any(), any());
+        messages.forEach((msg) -> verify(handler, times(1)).processRegularSessionMsg(ctx, msg));
+    }
+
+}
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