diff --git a/test/mmynapi_decode_tests.erl b/test/mmynapi_decode_tests.erl
index daced31..5fe7b1a 100644
--- a/test/mmynapi_decode_tests.erl
+++ b/test/mmynapi_decode_tests.erl
@@ -11,6 +11,37 @@ decode_header_test_() ->
                                     {<<"vsn">>, [2,0,1]}, 
                                     {<<"type">>, <<"req.sendsms">>}, 
                                     {<<"system">>, <<"mmyn">>}, 
-                                    {<<"transaction_id">>, <<"0xdeadbeef">>}]}))}
-   ].
+                                    {<<"transaction_id">>, <<"0xdeadbeef">>}]}))},
+        {"Error out when header JSON form is missing a 'vsn' field",
+            ?_assertEqual({error, no_version}, 
+                        mmynapi_decode:to_header({[ 
+                                    {<<"type">>, <<"req.sendsms">>}, 
+                                    {<<"system">>, <<"mmyn">>}, 
+                                    {<<"transaction_id">>, <<"0xdeadbeef">>}]}))},
+        {"Error out when header 'vsn' field is wrong",
+            ?_assertEqual({error, {wrong_msg_vsn, [{current_msg_vsn, [2,0,1]}, {parsed_msg_vsn,[3,2,1]}]}}, 
+                        mmynapi_decode:to_header({[ 
+                                    {<<"type">>, <<"req.sendsms">>}, 
+                                    {<<"vsn">>, [3,2,1]},
+                                    {<<"system">>, <<"mmyn">>}, 
+                                    {<<"transaction_id">>, <<"0xdeadbeef">>}]}))},
+        {"Error out when header JSON form is missing a 'type' field",
+            ?_assertEqual({error, no_type}, 
+                        mmynapi_decode:to_header({[ 
+                                    {<<"vsn">>, [2,0,1]}, 
+                                    {<<"system">>, <<"mmyn">>}, 
+                                    {<<"transaction_id">>, <<"0xdeadbeef">>}]}))},
+        {"Error out when header JSON form is missing a 'system' field",
+            ?_assertEqual({error, no_system}, 
+                        mmynapi_decode:to_header({[ 
+                                    {<<"vsn">>, [2,0,1]}, 
+                                    {<<"type">>, <<"res.sendsms">>},
+                                    {<<"transaction_id">>, <<"0xdeadbeef">>}]}))},
+        {"Error out when header JSON form is missing a 'transaction_id' field",
+            ?_assertEqual({error, no_transaction_id}, 
+                        mmynapi_decode:to_header({[ 
+                                    {<<"vsn">>, [2,0,1]}, 
+                                    {<<"system">>, <<"mmyn">>}, 
+                                    {<<"type">>, <<"res.sendsms">>}]}))} 
+    ].