diff --git a/package.json b/package.json
index e51db5bc..795f335a 100644
--- a/package.json
+++ b/package.json
@@ -23,6 +23,13 @@
     "typescript": "4.7.4",
     "web-vitals": "2.1.4"
   },
+  "jest": {
+    "collectCoverageFrom": [
+      "src/**/*.{js,jsx,ts,tsx}",
+      "!src/index.tsx",
+      "!src/test-utils/*"
+    ]
+  },
   "scripts": {
     "start": "react-scripts start",
     "build": "react-scripts build",
@@ -47,4 +54,4 @@
       "last 1 safari version"
     ]
   }
-}
\ No newline at end of file
+}
diff --git a/src/App.test.tsx b/src/App.test.tsx
index 838df452..a28519f5 100644
--- a/src/App.test.tsx
+++ b/src/App.test.tsx
@@ -1,7 +1,11 @@
-import { render } from "@testing-library/react";
-
+import { render, screen } from "@testing-library/react";
+import { Provider } from "react-redux";
 import App from "./App";
-
-test("renders learn react link", () => {
-  render(<App />);
+import { store } from "./store";
+test("renders App.tsx", () => {
+  render(
+    <Provider store={store}>
+      <App />
+    </Provider>
+  );
 });
diff --git a/src/components/Todo/Todo.test.tsx b/src/components/Todo/Todo.test.tsx
new file mode 100644
index 00000000..3bd26338
--- /dev/null
+++ b/src/components/Todo/Todo.test.tsx
@@ -0,0 +1,24 @@
+import { render, screen } from "@testing-library/react";
+import Todo from "./Todo";
+describe("<Todo />", () => {
+  it("should render without errors", () => {
+    render(<Todo title={"TODO_TITLE"} done={false} />);
+    //screen 으로 렌더링된 것을 접근
+    //getByText throws error when cannot find element
+    screen.getByText("TODO_TITLE"); // Implicit assertion
+    const doneButton = screen.getByText("Done"); // Implicit assertion
+    expect(doneButton).toBeInTheDocument(); // Explicit assertion
+  });
+  it("should render done mark when done is true", () => {
+    render(<Todo title={"TODO_TITLE"} done={true} />);
+    const title = screen.getByText("TODO_TITLE");
+    expect(title.classList.contains("done")).toBe(true);
+    screen.getByText("Undone");
+  });
+  it("should render undone mark when done is false", () => {
+    render(<Todo title={"TODO_TITLE"} done={false} />);
+    const title = screen.getByText("TODO_TITLE");
+    expect(title.classList.contains("done")).toBe(false);
+    screen.getByText("Done");
+  });
+});
diff --git a/src/components/TodoDetail/TodoDetail.test.tsx b/src/components/TodoDetail/TodoDetail.test.tsx
new file mode 100644
index 00000000..dcfff3d3
--- /dev/null
+++ b/src/components/TodoDetail/TodoDetail.test.tsx
@@ -0,0 +1,52 @@
+import { MemoryRouter, Navigate, Route, Routes } from "react-router";
+import { renderWithProviders } from "../../test-utils/mocks";
+import TodoDetail from "./TodoDetail";
+import { screen } from "@testing-library/react";
+import axios from "axios";
+
+const renderTodoDetail = () => {
+  //this is render
+  renderWithProviders(
+    <MemoryRouter>
+      <Routes>
+        <Route path="/todo-detail/:id" element={<TodoDetail />} />
+        <Route path="*" element={<Navigate to={"/todo-detail/3"} />} />
+      </Routes>
+    </MemoryRouter>,
+    {
+      preloadedState: {
+        todo: {
+          todos: [
+            {
+              id: 3,
+              title: "title3",
+              content: "content3",
+              done: false,
+            },
+          ],
+          selectedTodo: null,
+        },
+      },
+    }
+  );
+};
+
+describe("<TodoDetail/>", () => {
+  it("should render todo", async () => {
+    jest.spyOn(axios, "get").mockImplementation(() => {
+      return Promise.resolve({
+        data: {
+          id: 3,
+          title: "title3",
+          content: "content3",
+          done: false,
+        },
+      });
+    });
+    //render todo detail must happen after jest mocking
+    renderTodoDetail();
+    await screen.findByText("title3");
+    //only findbyDisplayValue works on await
+    await screen.findByText("content3");
+  });
+});
diff --git a/src/containers/TodoList/NewTodo/NewTodo.test.tsx b/src/containers/TodoList/NewTodo/NewTodo.test.tsx
new file mode 100644
index 00000000..0c47a784
--- /dev/null
+++ b/src/containers/TodoList/NewTodo/NewTodo.test.tsx
@@ -0,0 +1,62 @@
+import { fireEvent, screen, waitFor } from "@testing-library/react";
+import axios from "axios";
+import * as todoSlice from "../../../store/slices/todo";
+import { getMockStore, renderWithProviders } from "../../../test-utils/mocks";
+import NewTodo from "./NewTodo";
+
+const mockNavigate = jest.fn();
+
+jest.mock("react-router", () => ({
+  //그래야 NavLink 같은 걸 쓸 수 있다.
+  ...jest.requireActual("react-router"),
+  Navigate: (props: any) => {
+    //we need to check navigate to
+    mockNavigate(props.to);
+    return null;
+  },
+  useNavigate: () => mockNavigate,
+}));
+
+describe("the test of NewTodo", () => {
+  //branch submitted
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+  it("should render NewTodo", () => {
+    renderWithProviders(<NewTodo />);
+    screen.getByText("Add a Todo");
+  });
+  it("should change inputs on enter", async () => {
+    //this changes the dispatch return value
+    axios.post = jest.fn().mockResolvedValueOnce({
+      //this is the result value
+      data: {
+        id: 1,
+        title: "안녕하세요",
+        content: "내용 채우기",
+        done: false,
+      },
+    });
+    renderWithProviders(<NewTodo />);
+    const titleInput = screen.getByLabelText("Title");
+    const contentInput = screen.getByLabelText("Content");
+    const submitButton = screen.getByText("Submit");
+    fireEvent.change(titleInput, { target: { value: "안녕하세요" } });
+    fireEvent.change(contentInput, { target: { value: "내용 채우기" } });
+    await screen.findByDisplayValue("안녕하세요"); //test setstate
+    await screen.findByDisplayValue("내용 채우기"); //test setstate
+    fireEvent.click(submitButton);
+    //this waits for dispatch being called
+    await waitFor(() => expect(mockNavigate).toHaveBeenCalledWith("/todos"));
+  });
+  it("should alert when inputs are empty", async () => {
+    const mockPostTodo = jest.spyOn(todoSlice, "postTodo");
+    window.alert = jest.fn();
+    console.error = jest.fn();
+    axios.post = jest.fn().mockResolvedValueOnce(new Error());
+    renderWithProviders(<NewTodo />);
+    const submitButton = screen.getByText("Submit");
+    fireEvent.click(submitButton);
+    await waitFor(() => expect(window.alert).toBeCalled());
+  });
+});
diff --git a/src/containers/TodoList/NewTodo/NewTodo.tsx b/src/containers/TodoList/NewTodo/NewTodo.tsx
index ece2d4b8..3ec2e6ea 100644
--- a/src/containers/TodoList/NewTodo/NewTodo.tsx
+++ b/src/containers/TodoList/NewTodo/NewTodo.tsx
@@ -12,14 +12,6 @@ export default function NewTodo() {
   const [submitted, setSubmitted] = useState<boolean>(false);
   const dispatch = useDispatch<AppDispatch>();
 
-  // const navigate = useNavigate()
-  // const postTodoHandler = () => {
-  //   const data = { title: title, content: content };
-  //   alert("Submitted\n" + data.title + "\n" + data.content);
-  //   setSubmitted(true);
-  //   navigate('/todos')
-  // };
-
   const postTodoHandler = async () => {
     const data = { title: title, content: content };
     const result = await dispatch(postTodo(data));
@@ -38,11 +30,19 @@ export default function NewTodo() {
         <h1>Add a Todo</h1>
         <label>
           Title
-          <input type="text" value={title} onChange={(event) => setTitle(event.target.value)} />
+          <input
+            type="text"
+            value={title}
+            onChange={(event) => setTitle(event.target.value)}
+          />
         </label>
         <label>
           Content
-          <textarea rows={4} value={content} onChange={(event) => setContent(event.target.value)} />
+          <textarea
+            rows={4}
+            value={content}
+            onChange={(event) => setContent(event.target.value)}
+          />
         </label>
         <button onClick={() => postTodoHandler()}>Submit</button>
       </div>
diff --git a/src/containers/TodoList/TodoList.test.tsx b/src/containers/TodoList/TodoList.test.tsx
new file mode 100644
index 00000000..4487a0c8
--- /dev/null
+++ b/src/containers/TodoList/TodoList.test.tsx
@@ -0,0 +1,123 @@
+// containers/TodoList/TodoList.test.tsx
+import { IProps as TodoProps } from "../../components/Todo/Todo";
+import { fireEvent, render, screen } from "@testing-library/react";
+import { Provider } from "react-redux";
+import { MemoryRouter, Route, Routes } from "react-router";
+import { getMockStore } from "../../test-utils/mocks";
+import TodoList from "./TodoList";
+import { TodoState } from "../../store/slices/todo";
+
+jest.mock("../../components/Todo/Todo", () => (props: TodoProps) => (
+  //this data-testid is fake id
+  <div data-testid="spyTodo">
+    <div className="title" onClick={props.clickDetail}>
+      {props.title}
+    </div>
+    <button className="doneButton" onClick={props.clickDone}>
+      done
+    </button>
+    <button className="deleteButton" onClick={props.clickDelete}>
+      delete
+    </button>
+  </div>
+));
+
+const stubInitialState: TodoState = {
+  todos: [
+    {
+      id: 1,
+      title: "TODO_TEST_TITLE_1",
+      content: "TODO_TEST_CONTENT_1",
+      done: false,
+    },
+    {
+      id: 2,
+      title: "TODO_TEST_TITLE_2",
+      content: "TODO_TEST_CONTENT_2",
+      done: false,
+    },
+    {
+      id: 3,
+      title: "TODO_TEST_TITLE_3",
+      content: "TODO_TEST_CONTENT_3",
+      done: false,
+    },
+  ],
+  selectedTodo: null,
+};
+const mockStore = getMockStore({ todo: stubInitialState });
+
+const mockNavigate = jest.fn();
+
+//외부 dependency useNavigate
+jest.mock("react-router", () => ({
+  //그래야 NavLink 같은 걸 쓸 수 있다.
+  ...jest.requireActual("react-router"),
+  useNavigate: () => mockNavigate,
+}));
+const mockDispatch = jest.fn();
+
+//useDispatch mockign
+jest.mock("react-redux", () => ({
+  ...jest.requireActual("react-redux"),
+  //useDispatch만 우리가 mocking
+  useDispatch: () => mockDispatch,
+}));
+
+describe("<TodoList />", () => {
+  let todoList: JSX.Element;
+  beforeEach(() => {
+    //mock들을 다 지우기
+    jest.clearAllMocks();
+    todoList = (
+      <Provider store={mockStore}>
+        <MemoryRouter>
+          <Routes>
+            <Route
+              path="/"
+              element={<TodoList title="TODOLIST_TEST_TITLE" />}
+            />
+          </Routes>
+        </MemoryRouter>
+      </Provider>
+    );
+  });
+  it("should render TodoList", () => {
+    const { container } = render(todoList);
+    expect(container).toBeTruthy();
+  });
+  it("should render todos", () => {
+    render(todoList);
+    const todos = screen.getAllByTestId("spyTodo");
+    //initailly 3개 넣기로 했기 때문에 3개
+    expect(todos).toHaveLength(3);
+  });
+  it("should handle clickDetail", () => {
+    render(todoList);
+    const todos = screen.getAllByTestId("spyTodo");
+    const todo = todos[0];
+    // eslint-disable-next-line testing-library/no-node-access
+    const title = todo.querySelector(".title");
+    //querySelector는 class name을 이용해서 받음
+    fireEvent.click(title!);
+    expect(mockNavigate).toHaveBeenCalledTimes(1);
+  });
+  it("should handle clickDone", () => {
+    render(todoList);
+    const todos = screen.getAllByTestId("spyTodo");
+    const todo = todos[0];
+    // eslint-disable-next-line testing-library/no-node-access
+    const doneButton = todo.querySelector(".doneButton");
+    fireEvent.click(doneButton!);
+    expect(mockDispatch).toHaveBeenCalled();
+  });
+  it("should handle clickDelete", () => {
+    render(todoList);
+    const todos = screen.getAllByTestId("spyTodo");
+    const todo = todos[0];
+    // eslint-disable-next-line testing-library/no-node-access
+    const deleteButton = todo.querySelector(".deleteButton");
+    fireEvent.click(deleteButton!);
+    expect(mockDispatch).toHaveBeenCalled();
+  });
+});
diff --git a/src/store/slices/todo.test.ts b/src/store/slices/todo.test.ts
new file mode 100644
index 00000000..f9800575
--- /dev/null
+++ b/src/store/slices/todo.test.ts
@@ -0,0 +1,102 @@
+import { AnyAction, configureStore, EnhancedStore } from "@reduxjs/toolkit";
+import axios from "axios";
+import { ThunkMiddleware } from "redux-thunk";
+import reducer, { TodoState } from "./todo";
+import {
+  fetchTodos,
+  fetchTodo,
+  postTodo,
+  deleteTodo,
+  toggleDone,
+} from "./todo";
+
+describe("todo reducer", () => {
+  let store: EnhancedStore<
+    { todo: TodoState },
+    AnyAction,
+    [ThunkMiddleware<{ todo: TodoState }, AnyAction, undefined>]
+  >;
+  const fakeTodo = {
+    id: 1,
+    title: "test",
+    content: "test",
+    done: false,
+  };
+  beforeAll(() => {
+    store = configureStore({ reducer: { todo: reducer } });
+  }); // end beforeAll
+
+  it("should handle initial state", () => {
+    //reducer(state, action)
+    //store는 undefined
+    //초기 상태 잘 만드는지 확인
+    expect(reducer(undefined, { type: "unknown" })).toEqual({
+      //to Equal is sort of like deep Equal
+      todos: [],
+      selectedTodo: null,
+    });
+  });
+  it("should handle fetchTodos", async () => {
+    //axios는 외부 dependency이기에 mock을 한다
+    //axios.get을 mock 함수로 대체
+    axios.get = jest.fn().mockResolvedValue({ data: [fakeTodo] });
+    await store.dispatch(fetchTodos());
+    expect(store.getState().todo.todos).toEqual([fakeTodo]);
+  });
+
+  it("should handle fetchTodo", async () => {
+    axios.get = jest.fn().mockResolvedValue({ data: fakeTodo });
+    await store.dispatch(fetchTodo(1));
+    expect(store.getState().todo.selectedTodo).toEqual(fakeTodo);
+  });
+
+  it("should handle deleteTodo", async () => {
+    axios.delete = jest.fn().mockResolvedValue({ data: null });
+    await store.dispatch(deleteTodo(1));
+    expect(store.getState().todo.todos).toEqual([]);
+  });
+
+  it("should handle postTodo", async () => {
+    //spyOn은 mock과 똑같이 mock 함수를 만든다
+    jest.spyOn(axios, "post").mockResolvedValue({
+      data: fakeTodo,
+    });
+    await store.dispatch(postTodo({ title: "test", content: "test" }));
+    expect(store.getState().todo.todos).toEqual([fakeTodo]);
+  });
+
+  it("should handle toggleDone", async () => {
+    jest.spyOn(axios, "put").mockResolvedValue({
+      data: fakeTodo,
+    });
+    await store.dispatch(toggleDone(fakeTodo.id));
+    expect(
+      store.getState().todo.todos.find((v) => v.id === fakeTodo.id)?.done
+    ).toEqual(true);
+  });
+
+  it("should handle error on postTodo", async () => {
+    const mockConsoleError = jest.fn();
+    console.error = mockConsoleError;
+    jest.spyOn(axios, "post").mockRejectedValue({
+      response: { data: { title: ["error"] } },
+    });
+    await store.dispatch(postTodo({ title: "test", content: "test" }));
+    expect(mockConsoleError).toBeCalled();
+  });
+
+  it("should handle null on fetchTodo", async () => {
+    axios.get = jest.fn().mockResolvedValue({ data: null });
+    await store.dispatch(fetchTodo(1));
+    expect(store.getState().todo.selectedTodo).toEqual(null);
+  });
+
+  it("should handle not existing todo toggle", async () => {
+    const beforeState = store.getState().todo;
+    jest.spyOn(axios, "put").mockResolvedValue({
+      data: { ...fakeTodo, id: 10 },
+    });
+    await store.dispatch(toggleDone(2));
+    expect(store.getState().todo).toEqual(beforeState);
+  });
+}); // end describe
diff --git a/src/store/slices/todo.ts b/src/store/slices/todo.ts
index 5f1a2dce..a9e8104c 100644
--- a/src/store/slices/todo.ts
+++ b/src/store/slices/todo.ts
@@ -60,13 +60,10 @@ export const todoSlice = createSlice({
   name: "todo",
   initialState,
   reducers: {
-    getAll: (state, action: PayloadAction<{ todos: TodoType[] }>) => {},
-    getTodo: (state, action: PayloadAction<{ targetId: number }>) => {
-      const target = state.todos.find((td) => td.id === action.payload.targetId);
-      state.selectedTodo = target ?? null;
-    },
     toggleDone: (state, action: PayloadAction<{ targetId: number }>) => {
-      const todo = state.todos.find((value) => value.id === action.payload.targetId);
+      const todo = state.todos.find(
+        (value) => value.id === action.payload.targetId
+      );
       if (todo) {
         todo.done = !todo.done;
       }
@@ -77,7 +74,10 @@ export const todoSlice = createSlice({
       });
       state.todos = deleted;
     },
-    addTodo: (state, action: PayloadAction<{ id: number; title: string; content: string }>) => {
+    addTodo: (
+      state,
+      action: PayloadAction<{ id: number; title: string; content: string }>
+    ) => {
       const newTodo = {
         id: action.payload.id,
         title: action.payload.title,
diff --git a/src/test-utils/mocks.tsx b/src/test-utils/mocks.tsx
new file mode 100644
index 00000000..41b8d61f
--- /dev/null
+++ b/src/test-utils/mocks.tsx
@@ -0,0 +1,34 @@
+import { configureStore, PreloadedState } from "@reduxjs/toolkit";
+import { render, RenderOptions } from "@testing-library/react";
+import { PropsWithChildren } from "react";
+import { Provider } from "react-redux";
+import { AppStore, RootState } from "../store";
+import todoReducer from "../store/slices/todo";
+
+interface ExtendedRenderOptions extends Omit<RenderOptions, "queries"> {
+  preloadedState?: PreloadedState<RootState>;
+  store?: AppStore;
+}
+
+export const getMockStore = (preloadedState?: PreloadedState<RootState>) => {
+  return configureStore({
+    reducer: { todo: todoReducer },
+    preloadedState,
+  });
+};
+
+export function renderWithProviders(
+  ui: React.ReactElement,
+  {
+    preloadedState,
+    // Automatically create a store instance if no store was passed in
+    store = getMockStore(preloadedState),
+    ...renderOptions
+  }: ExtendedRenderOptions = {}
+) {
+  function Wrapper({ children }: PropsWithChildren): JSX.Element {
+    return <Provider store={store}>{children}</Provider>;
+  }
+  // Return an object with the store and all of RTL's query functions
+  return { store, ...render(ui, { wrapper: Wrapper, ...renderOptions }) };
+}