Attempt to fix satinizer error in unittesting.

Author: arobenko

comms/include/comms/protocol/ChecksumPrefixLayer.h

@@ -225,8 +225,6 @@ class ChecksumPrefixLayer : public
         using IterType = typename std::decay<decltype(iter)>::type;
         using Tag = typename std::iterator_traits<IterType>::iterator_category;
 
-        auto& thisObj = BaseImpl::thisLayer();
-        thisObj.prepareFieldForWrite(0, &msg, field);
         return writeInternal(field, msg, iter, size, std::forward<TNextLayerWriter>(nextLayerWriter), Tag());
     }
 
@@ -511,6 +509,7 @@ class ChecksumPrefixLayer : public
     {
         auto& thisObj = BaseImpl::thisLayer();
         auto checksumIter = iter;
+        thisObj.prepareFieldForWrite(0U, &msg, field);
         auto es = thisObj.writeField(&msg, field, iter, size);
         if (es != comms::ErrorStatus::Success) {
             return es;
@@ -556,6 +555,7 @@ class ChecksumPrefixLayer : public
         TWriter&& nextLayerWriter) const
     {
         auto& thisObj = BaseImpl::thisLayer();
+        thisObj.prepareFieldForWrite(0U, &msg, field);
         auto es = thisObj.writeField(&msg, field, iter, size);
         if (es != comms::ErrorStatus::Success) {
             return es;

comms/test/ChecksumPrefixLayer.th

@@ -458,7 +458,12 @@ void ChecksumPrefixLayerTestSuite::test7()
 void ChecksumPrefixLayerTestSuite::test8()
 {
     static const char Buf[] = {
-        static_cast<char>(0xab), static_cast<char>(0xcd), 0x06, 0x0, 0x3, MessageType1, 0x01, 0x02, static_cast<char>(0x3f)
+        static_cast<char>(0xab), static_cast<char>(0xcd), // sync
+        0x06, // checksum
+        0x0, 0x3, // size
+        MessageType1, // id
+        0x01, 0x02, //data
+        static_cast<char>(0x3f) // garbage
     };
 
     static const std::size_t BufSize = std::extent<decltype(Buf)>::value;