1. Add Todo

//todos Reducer
const todos = (state = [], action) => {
  switch (action.type) {
    case 'ADD_TODO':
      return [
        ...state,
        {
          id: action.id,
          text: action.text,
          completed: false
        }
      ];
    default:
      return state;
  }
};

// 测试 addTodo
const testAddTodo = () => {
  const stateBefore = [];
  const action = {
    type: 'ADD_TODO',
    id: 0,
    text: 'Learn Redux'
  };

  const stateAfter = [
    {
      id: 0,
      text: 'Learn Redux',
      completed: false
    }
  ];

  deepFreeze(stateBefore);
  deepFreeze(action);

  expect(
    todos(stateBefore, action)
  ).toEqual(stateAfter);
};


testAddTodo();

console.log('Test passed All.')

2. Toggle Todo

//todos Reducer
const todos = (state = [], action) => {
  switch (action.type) {
    case 'TOGGLE_TODO':
      return state.map(todo => {
        if (todo.id !== action.id) {
          return todo;
        }

        return {
          ...todo,
          completed: !todo.completed
        };
      });
    default:
      return state;
  }
};

// 测试 testToggleTodo
const testToggleTodo = () => {
  const stateBefore = [
    {
      id: 0,
      text: 'Learn Redux',
      completed: false
    },
    {
      id: 1,
      text: 'Go Shopping',
      completed: false
    }
  ];

  const action = {
    type: 'TOGGLE_TODO',
    id: 1
  };

  const stateAfter = [
    {
      id: 0,
      text: 'Learn Redux',
      completed: false
    },
    {
      id: 1,
      text: 'Go Shopping',
      completed: true
    }
  ];

  deepFreeze(stateBefore);
  deepFreeze(action);

  expect(
    todos(stateBefore, action)
  ).toEqual(stateAfter);
};

testToggleTodo();

console.log('Test passed All.')

//最终代码：http://jsbin.com/sunuwed/2/edit?html,js,output