test(ads): add unit tests for JSON extraction and LLM fallback functions

backend/ads/tests.py

@@ -102,3 +102,52 @@ class AdEvaluationAPITests(APITestCase):
         self.assertEqual(response.status_code, status.HTTP_204_NO_CONTENT)
         self.assertFalse(AdEvaluation.objects.filter(id=self.eval1.id).exists())
 
+
+from unittest.mock import MagicMock
+from ads.tasks import extract_and_parse_json, call_llm_with_structured_fallback, AdEvaluationResult
+
+class AdTasksHelperTests(APITestCase):
+    def test_extract_and_parse_json_raw(self):
+        raw = '{"is_flagged": true, "reason": "مناسب است", "confidence": 0.9}'
+        res = extract_and_parse_json(raw)
+        self.assertTrue(res['is_flagged'])
+        self.assertEqual(res['reason'], 'مناسب است')
+
+    def test_extract_and_parse_json_markdown_fence(self):
+        raw = '```json\n{\n  "is_flagged": false,\n  "reason": "نامناسب",\n  "confidence": 0.2\n}\n```'
+        res = extract_and_parse_json(raw)
+        self.assertFalse(res['is_flagged'])
+
+    def test_extract_and_parse_json_with_preamble(self):
+        raw = 'Here is the response:\n```json\n{"is_flagged": true, "reason": "خوب", "confidence": 0.8}\n```\nHope this helps!'
+        res = extract_and_parse_json(raw)
+        self.assertTrue(res['is_flagged'])
+
+    def test_call_llm_fallback_on_markdown(self):
+        mock_client = MagicMock()
+        # beta parse raises exception (simulating markdown parse failure)
+        mock_client.beta.chat.completions.parse.side_effect = Exception("Invalid JSON markdown")
+        
+        # standard completion returns markdown
+        mock_message = MagicMock()
+        mock_message.content = '```json\n{"is_flagged": true, "reason": "پرچم گذاری شد", "confidence": 0.95}\n```'
+        mock_choice = MagicMock()
+        mock_choice.message = mock_message
+        mock_completion = MagicMock()
+        mock_completion.choices = [mock_choice]
+        mock_client.chat.completions.create.return_value = mock_completion
+
+        res = call_llm_with_structured_fallback(
+            client=mock_client,
+            model_name="openrouter/free",
+            system_instruction="sys",
+            user_content="user",
+            pydantic_cls=AdEvaluationResult,
+            max_tokens=2500,
+            timeout=35
+        )
+        self.assertTrue(res.is_flagged)
+        self.assertEqual(res.reason, "پرچم گذاری شد")
+        self.assertEqual(res.confidence, 0.95)
+
+