add test case demonstrating rlp order dependence

model/encoding/rlp/rlp_test.go

@@ -0,0 +1,29 @@
+package rlp_test
+
+import (
+	"testing"
+
+	"github.com/onflow/go-ethereum/rlp"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// TestRLPStructFieldOrder tests the field ordering property of RLP encoding.
+// It provides evidence that RLP encoding depends on struct field ordering.
+func TestRLPStructFieldOrder(t *testing.T) {
+	a := struct {
+		A uint32 // A first
+		B uint32
+	}{A: 2, B: 3}
+
+	b := struct {
+		B uint32 // B first
+		A uint32
+	}{A: 2, B: 3}
+
+	abin, err := rlp.EncodeToBytes(a)
+	require.NoError(t, err)
+	bbin, err := rlp.EncodeToBytes(b)
+	require.NoError(t, err)
+	assert.NotEqual(t, abin, bbin)
+}