Add tests for get task serializer

todo/tests/unit/serializers/__init__.py

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+# Added this because without this file Django isn't able to auto detect the test files

todo/tests/unit/serializers/test_get_tasks_serializer.py

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+from unittest import TestCase
+from rest_framework.exceptions import ValidationError
+
+from todo.constants.task import DEFAULT_PAGE_LIMIT, MAX_PAGE_LIMIT
+from todo.serializers.get_tasks_serializer import GetTaskQueryParamsSerializer
+
+
+class GetTaskQueryParamsSerializerTest(TestCase):
+    def test_serializer_validates_and_returns_valid_input(self):
+        data = {"page": "2", "limit": "5"}
+        serializer = GetTaskQueryParamsSerializer(data=data)
+        self.assertTrue(serializer.is_valid())
+        self.assertEqual(serializer.validated_data["page"], 2)
+        self.assertEqual(serializer.validated_data["limit"], 5)
+
+    def test_serializer_applies_default_values_for_missing_fields(self):
+        serializer = GetTaskQueryParamsSerializer(data={})
+        self.assertTrue(serializer.is_valid())
+        self.assertEqual(serializer.validated_data["page"], 1)
+        self.assertEqual(serializer.validated_data["limit"], DEFAULT_PAGE_LIMIT)
+
+    def test_serializer_raises_error_for_page_below_min_value(self):
+        data = {"page": "0"}
+        serializer = GetTaskQueryParamsSerializer(data=data)
+        with self.assertRaises(ValidationError) as context:
+            serializer.is_valid(raise_exception=True)
+        self.assertIn("page must be greater than or equal to 1", str(context.exception))
+
+    def test_serializer_raises_error_for_limit_below_min_value(self):
+        data = {"limit": "0"}
+        serializer = GetTaskQueryParamsSerializer(data=data)
+        with self.assertRaises(ValidationError) as context:
+            serializer.is_valid(raise_exception=True)
+        self.assertIn("limit must be greater than or equal to 1", str(context.exception))
+
+    def test_serializer_raises_error_for_limit_above_max_value(self):
+        data = {"limit": f"{MAX_PAGE_LIMIT + 1}"}
+        serializer = GetTaskQueryParamsSerializer(data=data)
+        with self.assertRaises(ValidationError) as context:
+            serializer.is_valid(raise_exception=True)
+        self.assertIn(f"Ensure this value is less than or equal to {MAX_PAGE_LIMIT}", str(context.exception))
+
+    def test_serializer_handles_partial_input_gracefully(self):
+        data = {"page": "3"}
+        serializer = GetTaskQueryParamsSerializer(data=data)
+        self.assertTrue(serializer.is_valid())
+        self.assertEqual(serializer.validated_data["page"], 3)
+        self.assertEqual(serializer.validated_data["limit"], DEFAULT_PAGE_LIMIT)
+
+    def test_serializer_ignores_undefined_extra_fields(self):
+        data = {"page": "2", "limit": "5", "extra_field": "ignored"}
+        serializer = GetTaskQueryParamsSerializer(data=data)
+        self.assertTrue(serializer.is_valid())
+        self.assertEqual(serializer.validated_data["page"], 2)
+        self.assertEqual(serializer.validated_data["limit"], 5)
+        self.assertNotIn("extra_field", serializer.validated_data)