[test] add tests for the ToDoList class

.github/workflows/ci_for_todo.yml

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+# This is a basic workflow to help you get started with Actions
+
+name: CI
+
+# Controls when the workflow will run
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    types: [synchronize, opened, reopened, ready_for_review]
+
+  # Allows you to run this workflow manually from the Actions tab
+  workflow_dispatch:
+
+# A workflow run is made up of one or more jobs that can run sequentially or in parallel
+jobs:
+  # This workflow contains a single job called "build-and-run"
+  build-and-run:
+    # The type of runner that the job will run on
+    runs-on: ubuntu-latest
+
+    # Steps represent a sequence of tasks that will be executed as part of the job
+    steps:
+      # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
+      - uses: actions/checkout@v4
+
+      - name: Setup Python
+        uses: actions/[email protected]
+        with:
+          python-version: '3.12'
+
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install pytest
+
+      # Runs a set of commands using the runners shell
+      - name: Run ToDoList tests
+        shell: bash
+        run: |
+          pytest tests

tests/test_todo_list.py

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+import pytest
+from todo.todo_list import ToDoList
+
+def test_add_task():
+    todo = ToDoList()
+    task = "Write unit tests"
+    index = todo.add_task(task)
+    assert index == 0
+    assert todo.tasks == [task]
+
+def test_add_task_invalid():
+    todo = ToDoList()
+    with pytest.raises(ValueError, match="Task must be a non-empty string."):
+        todo.add_task("")  # Testing with an empty string
+
+def test_get_task():
+    todo = ToDoList()
+    task = "Write unit tests"
+    todo.add_task(task)
+    assert todo.get_task(0) == task
+
+def test_get_task_invalid_index():
+    todo = ToDoList()
+    with pytest.raises(IndexError, match="Task index out of range."):
+        todo.get_task(1)  # No task at index 1
+
+def test_remove_task():
+    todo = ToDoList()
+    task = "Write documentation"
+    todo.add_task(task)
+    removed_task = todo.remove_task(0)
+    assert removed_task == task
+    assert len(todo.tasks) == 0
+
+def test_remove_task_invalid_index():
+    todo = ToDoList()
+    with pytest.raises(IndexError, match="Task index out of range."):
+        todo.remove_task(0)  # No task to remove