Adds test for DeriveRoot function in trie (#691)

* Adds test for DeriveRoot function in trie

* Fix linter error

trie/derive_root_test.go

@@ -0,0 +1,37 @@
+package trie
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/vechain/thor/v2/thor"
+)
+
+type MockDerivableList struct {
+	Elements [][]byte
+}
+
+func (m *MockDerivableList) Len() int {
+	return len(m.Elements)
+}
+
+func (m *MockDerivableList) GetRlp(i int) []byte {
+	if i >= len(m.Elements) {
+		return nil
+	}
+	return m.Elements[i]
+}
+
+func TestDeriveRoot(t *testing.T) {
+	mockList := &MockDerivableList{
+		Elements: [][]byte{
+			{1, 2, 3, 4},
+			{1, 2, 3, 4, 5, 6},
+		},
+	}
+
+	root := DeriveRoot(mockList)
+
+	assert.Equal(t, "0x154227caf1172839284ce29cd6eaaee115af0993d5a5a4a08d9bb19ed18edae7", root.String())
+	assert.NotEqual(t, thor.Bytes32{}, root, "The root hash should not be empty")
+}