Add tests for task service (#5)

todo/tests/unit/services/__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/services/test_task_service.py

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+from unittest.mock import Mock, patch
+from unittest import TestCase
+
+from todo.dto.responses.get_tasks_response import GetTasksResponse
+from todo.dto.responses.paginated_response import LinksData
+from todo.dto.user_dto import UserDTO
+from todo.services.task_service import TaskService
+from todo.dto.task_dto import TaskDTO
+from todo.tests.fixtures.task_model import tasks_models
+from todo.tests.fixtures.label_model import label_models
+
+
+class TaskServiceTests(TestCase):
+    @patch("todo.services.task_service.reverse_lazy", return_value="/v1/tasks")
+    def setUp(self, mock_reverse_lazy):
+        self.mock_reverse_lazy = mock_reverse_lazy
+
+    @patch("todo.services.task_service.TaskRepository.count")
+    @patch("todo.services.task_service.TaskRepository.list")
+    @patch("todo.services.task_service.LabelRepository.list_by_ids")
+    def test_get_tasks_returns_paginated_response(
+        self, mock_label_repo: Mock, mock_task_repo: Mock, mock_task_count: Mock
+    ):
+        mock_task_repo.return_value = [tasks_models[0]]
+        mock_label_repo.return_value = label_models
+        mock_task_count.return_value = 5
+
+        response: GetTasksResponse = TaskService.get_tasks(2, 1)
+        self.assertIsInstance(response, GetTasksResponse)
+        self.assertEqual(len(response.tasks), 1)
+
+        self.assertIsInstance(response.links, LinksData)
+        self.assertEqual(response.links.next, f"{self.mock_reverse_lazy("tasks")}?page=3&limit=1")
+        self.assertEqual(response.links.prev, f"{self.mock_reverse_lazy("tasks")}?page=1&limit=1")
+
+    @patch("todo.services.task_service.TaskRepository.count")
+    @patch("todo.services.task_service.TaskRepository.list")
+    @patch("todo.services.task_service.LabelRepository.list_by_ids")
+    def test_get_tasks_doesnt_returns_prev_link_for_first_page(
+        self, mock_label_repo: Mock, mock_task_repo: Mock, mock_task_count: Mock
+    ):
+        mock_task_repo.return_value = [tasks_models[0]]
+        mock_label_repo.return_value = label_models
+        mock_task_count.return_value = 10
+
+        response: GetTasksResponse = TaskService.get_tasks(1, 1)
+
+        self.assertIsNone(response.links.prev)
+
+    @patch("todo.services.task_service.TaskRepository.count")
+    def test_get_tasks_returns_zero_tasks_if_no_tasks_present(self, mock_task_count: Mock):
+        mock_task_count.return_value = 5
+
+        response: GetTasksResponse = TaskService.get_tasks(2, 10)
+        self.assertIsInstance(response, GetTasksResponse)
+        self.assertEqual(len(response.tasks), 0)
+        self.assertIsNone(response.links)
+
+    @patch("todo.services.task_service.LabelRepository.list_by_ids")
+    def test_prepare_task_dto_maps_model_to_dto(self, mock_label_repo: Mock):
+        task_model = tasks_models[0]
+        mock_label_repo.return_value = label_models
+
+        result: TaskDTO = TaskService.prepare_task_dto(task_model)
+
+        mock_label_repo.assert_called_once_with(task_model.labels)
+
+        self.assertIsInstance(result, TaskDTO)
+        self.assertEqual(result.id, str(task_model.id))
+
+    def test_prepare_user_dto_maps_model_to_dto(self):
+        user_id = tasks_models[0].assignee
+        result: UserDTO = TaskService.prepare_user_dto(user_id)
+
+        self.assertIsInstance(result, UserDTO)
+        self.assertEqual(result.id, user_id)
+        self.assertEqual(result.name, "SYSTEM")