diff --git a/murano/dsl/helpers.py b/murano/dsl/helpers.py
index 7eed7509..47e871f7 100644
--- a/murano/dsl/helpers.py
+++ b/murano/dsl/helpers.py
@@ -73,12 +73,7 @@ def evaluate(value, context, freeze=True):
 def merge_lists(list1, list2):
     result = []
     for item in list1 + list2:
-        exists = False
-        for old_item in result:
-            if item == old_item:
-                exists = True
-                break
-        if not exists:
+        if item not in result:
             result.append(item)
     return result
 
diff --git a/murano/tests/unit/dsl/test_helpers.py b/murano/tests/unit/dsl/test_helpers.py
index b81968c4..fb25c0fd 100644
--- a/murano/tests/unit/dsl/test_helpers.py
+++ b/murano/tests/unit/dsl/test_helpers.py
@@ -15,29 +15,43 @@ from murano.dsl import helpers
 from murano.tests.unit import base
 
 
-class TestHeatStack(base.MuranoTestCase):
-    def test_merge_dicts(self):
-        dict1 = {"resource": "test"}
-        dict2 = {"description": "Test merge dicts"}
+class TestMergeDicts(base.MuranoTestCase):
+    def check(self, dict1, dict2, expected):
         result = helpers.merge_dicts(dict1, dict2)
-        expected = {"resource": "test",
-                    "description": "Test merge dicts"}
         self.assertEqual(expected, result)
 
-        dict2 = {"resource": None, "description": "Test merge dicts"}
-        result = helpers.merge_dicts(dict1, dict2)
-        expected = {"resource": "test",
-                    "description": "Test merge dicts"}
-        self.assertEqual(expected, result)
+    def test_dicts_plain(self):
+        dict1 = {"a": "1"}
+        dict2 = {"a": "100", "ab": "12"}
+        expected = {"a": "100", "ab": "12"}
+        self.check(dict1, dict2, expected)
 
-        dict2 = {"resource": "abc", "description": "Test merge dicts"}
-        self.assertEqual(expected, result)
+    def test_different_types_none(self):
+        dict1 = {"a": "1"}
+        dict2 = {"a": None, "ab": "12"}
+        expected = {"a": "1", "ab": "12"}
+        self.check(dict1, dict2, expected)
 
-        dict2 = {"resource": {"test": 1}}
+    def test_different_types_of_iterable(self):
+        dict1 = {"a": {"ab": "1"}}
+        dict2 = {"a": ["ab", "1"]}
         self.assertRaises(TypeError, helpers.merge_dicts, dict1, dict2)
 
-        dict1 = {"resource": None}
-        dict2 = {"resource": "test", "description": "Test merge dicts"}
-        expected = {"resource": None, "description": "Test merge dicts"}
-        result = helpers.merge_dicts(dict1, dict2)
+    def test_merge_nested_dicts(self):
+        dict1 = {"a": {"ab": {}, "abc": "1"}}
+        dict2 = {"a": {"abc": "123"}}
+        expected = {"a": {"ab": {}, "abc": "123"}}
+        self.check(dict1, dict2, expected)
+
+    def test_merge_nested_dicts_with_max_levels(self):
+        dict1 = {"a": {"ab": {"abcd": "1234"}, "abc": "1"}}
+        dict2 = {"a": {"ab": {"y": "9"}, "abc": "123"}}
+        expected = {"a": {"ab": {"y": "9"}, "abc": "123"}}
+        result = helpers.merge_dicts(dict1, dict2, max_levels=2)
         self.assertEqual(expected, result)
+
+    def test_merge_with_lists(self):
+        dict1 = {"a": [1, 2]}
+        dict2 = {"a": [1, 3, 2, 4]}
+        expected = {"a": [1, 2, 3, 4]}
+        self.check(dict1, dict2, expected)