05_reducer_composition.js

// http://jsbin.com/xoganemojo/8/edit?js,console

const todos = (state = [], action) => {
      switch (action.type) {
        case 'ADD_TODO':
          return [
            ...state,
            {
              id: action.id,
              text: action.text,
              completed: false
            }
          ];
        case 'TOGGLE_TODO':
          return state.map((todo) => {
            if (todo.id !== action.id) {
              return todo;
            }
            
            return {
              ...todo,
              completed: !todo.completed
            };
          });
        default:
          return state;
      }
};

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);
};

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);
};

testAddTodo();
testToggleTodo();
console.log('All tests passed!');