Fix broken unit tests

Frameworks/MQTTnet.NetStandard/Serializer/MqttPacketReader.cs

@@ -24,14 +24,17 @@ namespace MQTTnet.Serializer
 
         public static async Task<MqttPacketHeader> ReadHeaderFromSourceAsync(Stream stream, CancellationToken cancellationToken)
         {
-            byte[] singleByteBuf = new byte[1];
-            var readCount = await stream.ReadAsync(singleByteBuf, 0, singleByteBuf.Length).ConfigureAwait(false);
+            // Wait for the next package which starts with the header. At this point there will probably
+            // some large delay and thus the thread should be put back to the pool (await). So ReadByte()
+            // is not an option here.
+            var buffer = new byte[1];
+            var readCount = await stream.ReadAsync(buffer, 0, 1, cancellationToken).ConfigureAwait(false);
             if (readCount <= 0)
             {
                 return null;
             }
 
-            var fixedHeader = singleByteBuf[0];
+            var fixedHeader = buffer[0];
             var controlPacketType = (MqttControlPacketType)(fixedHeader >> 4);
             var bodyLength = await ReadBodyLengthFromSourceAsync(stream, cancellationToken).ConfigureAwait(false);
 
@@ -88,8 +91,7 @@ namespace MQTTnet.Serializer
             var value = 0;
             byte encodedByte;
 
-            byte[] singleByteBuf = new byte[1];
-
+            var buffer = new byte[1];
             var readBytes = new List<byte>();
             do
             {
@@ -98,13 +100,13 @@ namespace MQTTnet.Serializer
                     throw new TaskCanceledException();
                 }
 
-                int readCount = await stream.ReadAsync(singleByteBuf, 0, singleByteBuf.Length).ConfigureAwait(false);
+                var readCount = await stream.ReadAsync(buffer, 0, 1, cancellationToken).ConfigureAwait(false);
                 if (readCount <= 0)
                 {
                     throw new MqttCommunicationException("Connection closed while reading remaining length data.");
                 }
 
-                encodedByte = singleByteBuf[0];
+                encodedByte = buffer[0];
                 readBytes.Add(encodedByte);
 
                 value += (byte)(encodedByte & 127) * multiplier;