Add test case for Http2StreamChannelId. (#10108)

Motivation:

Http2StreamChannelId is Serializable. A test case is needed to ensure that it works.

Modification:

Add a test case about serialization.

Result:

Improve test coverage slightly.

codec-http2/src/test/java/io/netty/handler/codec/http2/Http2StreamChannelIdTest.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright 2020 The Netty Project
+ *
+ * The Netty Project licenses this file to you 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 io.netty.handler.codec.http2;
+
+import java.io.IOException;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+
+import org.junit.Test;
+
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.ByteBufInputStream;
+import io.netty.buffer.ByteBufOutputStream;
+import io.netty.buffer.Unpooled;
+import io.netty.channel.ChannelId;
+import io.netty.channel.DefaultChannelId;
+
+import static org.junit.Assert.*;
+
+public class Http2StreamChannelIdTest {
+
+    @Test
+    public void testSerialization() throws Exception {
+        ChannelId normalInstance = new Http2StreamChannelId(DefaultChannelId.newInstance(), 0);
+
+        ByteBuf buf = Unpooled.buffer();
+        ObjectOutputStream outStream = new ObjectOutputStream(new ByteBufOutputStream(buf));
+        try {
+            outStream.writeObject(normalInstance);
+        } finally {
+            outStream.close();
+        }
+
+        ObjectInputStream inStream = new ObjectInputStream(new ByteBufInputStream(buf, true));
+        final ChannelId deserializedInstance;
+        try {
+            deserializedInstance = (ChannelId) inStream.readObject();
+        } finally {
+            inStream.close();
+        }
+
+        assertEquals(normalInstance, deserializedInstance);
+        assertEquals(normalInstance.hashCode(), deserializedInstance.hashCode());
+        assertEquals(0, normalInstance.compareTo(deserializedInstance));
+        assertEquals(normalInstance.asLongText(), deserializedInstance.asLongText());
+        assertEquals(normalInstance.asShortText(), deserializedInstance.asShortText());
+    }
+}