Scenic City Summit 2017: Get Started with Redux

Transcript

1. Jeremy Fairbank @elpapapollo / jfairbank Get Started with Redux
2. Software is broken. We are here to fix it. Say hi@testdouble.com
3. The Wild West of State
4. <div data-id="42" data-name="Tucker"> ... </div> var $el = $('[data-id="42"]'); var currentName = $el.data('name'); $el.data('name', currentName.toUpperCase()); Data in the DOM
5. Controller View Model Model Model Model Model View View View View MVC
6. View Model Model Model Model Model View Model View Model View Model View Model Model Two-way Data Binding
7. The Wild West of State State is everywhere and anyone can change it!
8. Predictable State Container
9. All application state in one place State Container
10. Predictable Old State REDUCER New State
11. Predictable Old State REDUCER New State • State changes in one place
12. Predictable Old State REDUCER New State • State changes in one place • State changes in well-defined ways
13. Predictable Old State REDUCER New State • State changes in one place • State changes in well-defined ways • Changes are serialized
14. Reducer View State Actions
15. Reducer View State Actions
16. Reducer View React, Angular, Vue, Vanilla JS, etc. State Actions
17. Reducer View State Actions Dispatch
18. Reducer View State Actions
19. <button id="decrement">-</button> <div id="counter">0</div> <button id="increment">+</button>
20. incrementBtn.addEventListener('click', () => { counter.innerText = Number(counter.innerText) + 1; }); decrementBtn.addEventListener('click', () => { counter.innerText = Number(counter.innerText) - 1; });
21. let state = 0; function render() { counter.innerText = state; } incrementBtn.addEventListener('click', () => { state += 1; render(); }); decrementBtn.addEventListener('click', () => { state -= 1; render(); });
22. let state = 0; function render() { counter.innerText = state; } incrementBtn.addEventListener('click', () => { state += 1; render(); }); decrementBtn.addEventListener('click', () => { state -= 1; render(); });
23. let state = 0; function render() { counter.innerText = state; } incrementBtn.addEventListener('click', () => { state += 1; render(); }); decrementBtn.addEventListener('click', () => { state -= 1; render(); });
24. let state = 0; function render() { counter.innerText = state; } incrementBtn.addEventListener('click', () => { state += 1; render(); }); decrementBtn.addEventListener('click', () => { state -= 1; render(); });
25. state += 1; state -= 1; Anyone can access and mutate state
26. state += 1 state -= 1 { type: 'INCREMENT' } { type: 'DECREMENT' } Tokens/descriptors that describe a type of change. Actions
27. function reducer(state = 0, action) { switch (action.type) { case 'INCREMENT': return state + 1; case 'DECREMENT': return state - 1; default: return state; } } Returns new state from current state and action. Reducer
28. function reducer(state = 0, action) { switch (action.type) { case 'INCREMENT': return state + 1; case 'DECREMENT': return state - 1; default: return state; } } Returns new state from current state and action. Reducer
29. function reducer(state = 0, action) { switch (action.type) { case 'INCREMENT': return state + 1; case 'DECREMENT': return state - 1; default: return state; } } Returns new state from current state and action. Reducer
30. function reducer(state = 0, action) { switch (action.type) { case 'INCREMENT': return state + 1; case 'DECREMENT': return state - 1; default: return state; } } Returns new state from current state and action. Reducer
31. function reducer(state = 0, action) { switch (action.type) { case 'INCREMENT': return state + 1; case 'DECREMENT': return state - 1; default: return state; } } Returns new state from current state and action. Reducer
32. function reducer(state = 0, action) { switch (action.type) { case 'INCREMENT': return state + 1; case 'DECREMENT': return state - 1; default: return state; } } Returns new state from current state and action. Reducer
33. function reducer(state = 0, action) { switch (action.type) { case 'INCREMENT': return state + 1; case 'DECREMENT': return state - 1; default: return state; } } Returns new state from current state and action. Reducer
34. Updating state is just a function call now let state = 0; state = reducer(state, { type: 'INCREMENT' }); // 1 state = reducer(state, { type: 'INCREMENT' }); // 2 state = reducer(state, { type: 'DECREMENT' }); // 1 state = reducer(state, { type: 'ADD_2' }); // 1 console.log(state); // 1
35. Updating state is just a function call now let state = 0; state = reducer(state, { type: 'INCREMENT' }); // 1 state = reducer(state, { type: 'INCREMENT' }); // 2 state = reducer(state, { type: 'DECREMENT' }); // 1 state = reducer(state, { type: 'ADD_2' }); // 1 console.log(state); // 1 Unhandled types are ignored
36. function dispatch(action) { state = reducer(state, action); render(); } incrementBtn.addEventListener('click', () => { dispatch({ type: 'INCREMENT' }); }); decrementBtn.addEventListener('click', () => { dispatch({ type: 'DECREMENT' }); }); Decouple event from state change.
37. function dispatch(action) { state = reducer(state, action); render(); } incrementBtn.addEventListener('click', () => { dispatch({ type: 'INCREMENT' }); }); decrementBtn.addEventListener('click', () => { dispatch({ type: 'DECREMENT' }); }); Decouple event from state change.
38. function dispatch(action) { state = reducer(state, action); render(); } incrementBtn.addEventListener('click', () => { dispatch({ type: 'INCREMENT' }); }); decrementBtn.addEventListener('click', () => { dispatch({ type: 'DECREMENT' }); }); Decouple event from state change.
39. function dispatch(action) { state = reducer(state, action); render(); } incrementBtn.addEventListener('click', () => { dispatch({ type: 'INCREMENT' }); }); decrementBtn.addEventListener('click', () => { dispatch({ type: 'DECREMENT' }); }); Decouple event from state change.
40. function dispatch(action) { state = reducer(state, action); render(); } incrementBtn.addEventListener('click', () => { dispatch({ type: 'INCREMENT' }); }); decrementBtn.addEventListener('click', () => { dispatch({ type: 'DECREMENT' }); }); Decouple event from state change.
41. STORE
42. import { createStore } from 'redux'; const store = createStore(reducer, 0); store.getState(); // 0
43. import { createStore } from 'redux'; const store = createStore(reducer, 0); store.getState(); // 0
44. import { createStore } from 'redux'; const store = createStore(reducer, 0); store.getState(); // 0
45. import { createStore } from 'redux'; const store = createStore(reducer, 0); store.getState(); // 0
46. import { createStore } from 'redux'; const store = createStore(reducer, 0); store.getState(); // 0
47. incrementBtn.addEventListener('click', () => { store.dispatch({ type: 'INCREMENT' }); }); decrementBtn.addEventListener('click', () => { store.dispatch({ type: 'DECREMENT' }); }); store.subscribe(() => { counter.innerText = store.getState(); });
48. incrementBtn.addEventListener('click', () => { store.dispatch({ type: 'INCREMENT' }); }); decrementBtn.addEventListener('click', () => { store.dispatch({ type: 'DECREMENT' }); }); store.subscribe(() => { counter.innerText = store.getState(); });
49. incrementBtn.addEventListener('click', () => { store.dispatch({ type: 'INCREMENT' }); }); decrementBtn.addEventListener('click', () => { store.dispatch({ type: 'DECREMENT' }); }); store.subscribe(() => { counter.innerText = store.getState(); });
50. Store Reducer State View 0
51. Store Reducer State View 0
52. Store Reducer State View 0 getState
53. Store Reducer View State 0
54. Store Reducer View State 0 INCREMENT dispatch
55. Store Reducer View State 0 INCREMENT dispatch
56. Store Reducer View State 0
57. Store Reducer View State 1
58. Store Reducer View State 1
59. Store Reducer View State 1 1 subscribe getState
60. incrementBtn.addEventListener('click', () => { store.dispatch({ type: 'INCREMENT' }); }); decrementBtn.addEventListener('click', () => { store.dispatch({ type: 'DECREMENT' }); }); Problems: • Creating actions are cumbersome • Requires direct access to store
61. const increment = () => ({ type: 'INCREMENT', }); const decrement = () => ({ type: 'DECREMENT', }); Reusable functions that create actions Action Creators
62. const increment = () => ({ type: 'INCREMENT', }); const decrement = () => ({ type: 'DECREMENT', }); Reusable functions that create actions Action Creators
63. const increment = () => ({ type: 'INCREMENT', }); const decrement = () => ({ type: 'DECREMENT', }); Reusable functions that create actions Action Creators
64. incrementBtn.addEventListener('click', () => { store.dispatch(increment()); }); decrementBtn.addEventListener('click', () => { store.dispatch(decrement()); }); Problems: • Creating actions are cumbersome • Requires direct access to store
65. const actions = { increment: () => store.dispatch(increment()), decrement: () => store.dispatch(decrement()), }; Automatically dispatch when invoked Bound Action Creators
66. const actions = { increment: () => store.dispatch(increment()), decrement: () => store.dispatch(decrement()), }; Automatically dispatch when invoked Bound Action Creators Manually created
67. const actions = { increment: () => store.dispatch(increment()), decrement: () => store.dispatch(decrement()), }; Automatically dispatch when invoked Bound Action Creators
68. import { bindActionCreators } from 'redux'; const actions = bindActionCreators( { increment, decrement }, store.dispatch ); Automatically dispatch when invoked Bound Action Creators
69. import { bindActionCreators } from 'redux'; const actions = bindActionCreators( { increment, decrement }, store.dispatch ); Automatically dispatch when invoked Bound Action Creators
70. import { bindActionCreators } from 'redux'; const actions = bindActionCreators( { increment, decrement }, store.dispatch ); Automatically dispatch when invoked Bound Action Creators Automatically created
71. Problems: • Creating actions are cumbersome • Requires direct access to store incrementBtn.addEventListener('click', actions.increment); decrementBtn.addEventListener('click', actions.decrement);
72. React +
73. github.com/reactjs/react-redux npm install --save react-redux Official React bindings for Redux React Redux Library
74. Reducer State Actions React Redux
75. React Redux React Application
76. React Redux React Application Provider
77. Component React Redux React Application Provider connect State Action Creators
78. Component Child React Redux React Application Provider connect State Child Action Creators
79. const MyApp = () => ( <div> <button>-</button> <div>0</div> <button>+</button> </div> );
80. import React from 'react'; import { render } from 'react-dom'; import { Provider } from 'react-redux'; render(( <Provider store={store}> <MyAppContainer /> </Provider> ), document.getElementById('main'));
81. import React from 'react'; import { render } from 'react-dom'; import { Provider } from 'react-redux'; render(( <Provider store={store}> <MyAppContainer /> </Provider> ), document.getElementById('main'));
82. import React from 'react'; import { render } from 'react-dom'; import { Provider } from 'react-redux'; render(( <Provider store={store}> <MyAppContainer /> </Provider> ), document.getElementById('main'));
83. import { connect } from 'react-redux'; const mapStateToProps = counter => ({ counter }); function mapDispatchToProps(dispatch) { return bindActionCreators({ onIncrement: increment, onDecrement: decrement, }, dispatch); } const MyAppContainer = connect( mapStateToProps, mapDispatchToProps )(MyApp);
84. import { connect } from 'react-redux'; const mapStateToProps = counter => ({ counter }); function mapDispatchToProps(dispatch) { return bindActionCreators({ onIncrement: increment, onDecrement: decrement, }, dispatch); } const MyAppContainer = connect( mapStateToProps, mapDispatchToProps )(MyApp);
85. import { connect } from 'react-redux'; const mapStateToProps = counter => ({ counter }); function mapDispatchToProps(dispatch) { return bindActionCreators({ onIncrement: increment, onDecrement: decrement, }, dispatch); } const MyAppContainer = connect( mapStateToProps, mapDispatchToProps )(MyApp);
86. import { connect } from 'react-redux'; const mapStateToProps = counter => ({ counter }); function mapDispatchToProps(dispatch) { return bindActionCreators({ onIncrement: increment, onDecrement: decrement, }, dispatch); } const MyAppContainer = connect( mapStateToProps, mapDispatchToProps )(MyApp);
87. import { connect } from 'react-redux'; const mapStateToProps = counter => ({ counter }); function mapDispatchToProps(dispatch) { return bindActionCreators({ onIncrement: increment, onDecrement: decrement, }, dispatch); } const MyAppContainer = connect( mapStateToProps, mapDispatchToProps )(MyApp);
88. const MyApp = (props) => ( <div> <button onClick={props.onDecrement}> - </button> <div>{props.counter}</div> <button onClick={props.onIncrement}> + </button> </div> );
89. const MyApp = (props) => ( <div> <button onClick={props.onDecrement}> - </button> <div>{props.counter}</div> <button onClick={props.onIncrement}> + </button> </div> ); Store state mapStateToProps
90. const MyApp = (props) => ( <div> <button onClick={props.onDecrement}> - </button> <div>{props.counter}</div> <button onClick={props.onIncrement}> + </button> </div> ); Bound action creators mapDispatchToProps
91. Immutable Object State
92. const initialState = { counter: 0, car: { color: 'red', }, };
93. const initialState = { counter: 0, car: { color: 'red', }, };
94. const initialState = { counter: 0, car: { color: 'red', }, };
95. const increment = () => ({ type: 'INCREMENT', }); const decrement = () => ({ type: 'DECREMENT', }); const changeColor = color => ({ type: 'CHANGE_COLOR', payload: color, });
96. const increment = () => ({ type: 'INCREMENT', }); const decrement = () => ({ type: 'DECREMENT', }); const changeColor = color => ({ type: 'CHANGE_COLOR', payload: color, });
97. const increment = () => ({ type: 'INCREMENT', }); const decrement = () => ({ type: 'DECREMENT', }); const changeColor = color => ({ type: 'CHANGE_COLOR', payload: color, });
98. function reducer(state = initialState, action) { switch (action.type) { case 'INCREMENT': return { ...state, counter: state.counter + 1 }; case 'DECREMENT': return { ...state, counter: state.counter - 1 }; case 'CHANGE_COLOR': return { ...state, car: { color: action.payload } }; default: return state; } }
99. function reducer(state = initialState, action) { switch (action.type) { case 'INCREMENT': return { ...state, counter: state.counter + 1 }; case 'DECREMENT': return { ...state, counter: state.counter - 1 }; case 'CHANGE_COLOR': return { ...state, car: { color: action.payload } }; default: return state; } }
100. function reducer(state = initialState, action) { switch (action.type) { case 'INCREMENT': return { ...state, counter: state.counter + 1 }; case 'DECREMENT': return { ...state, counter: state.counter - 1 }; case 'CHANGE_COLOR': return { ...state, car: { color: action.payload } }; default: return state; } }
101. function reducer(state = initialState, action) { switch (action.type) { case 'INCREMENT': return { ...state, counter: state.counter + 1 }; case 'DECREMENT': return { ...state, counter: state.counter - 1 }; case 'CHANGE_COLOR': return { ...state, car: { color: action.payload } }; default: return state; } }
102. function reducer(state = initialState, action) { switch (action.type) { case 'INCREMENT': return { ...state, counter: state.counter + 1 }; case 'DECREMENT': return { ...state, counter: state.counter - 1 }; case 'CHANGE_COLOR': return { ...state, car: { color: action.payload } }; default: return state; } }
103. function reducer(state = initialState, action) { switch (action.type) { case 'INCREMENT': return { ...state, counter: state.counter + 1 }; case 'DECREMENT': return { ...state, counter: state.counter - 1 }; case 'CHANGE_COLOR': return { ...state, car: { color: action.payload } }; default: return state; } }
104. store.subscribe(() => { console.log('state =', store.getState()); }); store.dispatch(increment()); store.dispatch(changeColor('green')); // state = { counter: 1, car: { color: 'red' } } // state = { counter: 1, car: { color: 'green' } }
105. store.subscribe(() => { console.log('state =', store.getState()); }); store.dispatch(increment()); store.dispatch(changeColor('green')); // state = { counter: 1, car: { color: 'red' } } // state = { counter: 1, car: { color: 'green' } }
106. store.subscribe(() => { console.log('state =', store.getState()); }); store.dispatch(increment()); store.dispatch(changeColor('green')); // state = { counter: 1, car: { color: 'red' } } // state = { counter: 1, car: { color: 'green' } }
107. function reducer(state = initialState, action) { }
108. Reducer Composition Create modular reducers for better organization and readability
109. Root Reducer Counter Reducer Car Reducer
110. function counterReducer(state = 0, action) { switch (action.type) { case 'INCREMENT': return state + 1; case 'DECREMENT': return state - 1; default: return state; } }
111. const initialState = { color: 'red' }; function carReducer(state = initialState, action) { switch (action.type) { case 'CHANGE_COLOR': return { ...state, color: action.payload }; default: return state; } }
112. const initialState = { color: 'red' }; function carReducer(state = initialState, action) { switch (action.type) { case 'CHANGE_COLOR': return { ...state, color: action.payload }; default: return state; } }
113. const initialState = { color: 'red' }; function carReducer(state = initialState, action) { switch (action.type) { case 'CHANGE_COLOR': return { ...state, color: action.payload }; default: return state; } }
114. function reducer(state = {}, action) { return { counter: counterReducer(state.counter, action), car: carReducer(state.car, action), }; }
115. function reducer(state = {}, action) { return { counter: counterReducer(state.counter, action), car: carReducer(state.car, action), }; }
116. function reducer(state = {}, action) { return { counter: counterReducer(state.counter, action), car: carReducer(state.car, action), }; }
117. function reducer(state = {}, action) { return { counter: counterReducer(state.counter, action), car: carReducer(state.car, action), }; }
118. import { combineReducers } from 'redux'; const reducer = combineReducers({ counter: counterReducer, car: carReducer, });
119. import { combineReducers } from 'redux'; const reducer = combineReducers({ counter: counterReducer, car: carReducer, });
120. import { combineReducers } from 'redux'; const reducer = combineReducers({ counter: counterReducer, car: carReducer, });
121. Root Reducer Counter Reducer Car Reducer Engine Reducer Tire Reducer … … …
122. Root Reducer Counter Reducer Car Reducer Engine Reducer Tire Reducer … … …
123. Root Reducer Counter Reducer Car Reducer Engine Reducer Tire Reducer … … …
124. Interact with APIs?
125. Middleware Enhance Redux applications
126. • Logging Middleware Enhance Redux applications
127. • Logging • Debugging Middleware Enhance Redux applications
128. • Logging • Debugging • API interaction Middleware Enhance Redux applications
129. • Logging • Debugging • API interaction • Custom actions Middleware Enhance Redux applications
130. Reducer View State Actions Middleware
131. Reducer View State Actions Middleware Intercept
132. const logMiddleware = api => next => action => { console.log('dispatch', action); const result = next(action); console.log('state =', api.getState()); return result; };
133. const logMiddleware = api => next => action => { console.log('dispatch', action); const result = next(action); console.log('state =', api.getState()); return result; };
134. const logMiddleware = api => next => action => { console.log('dispatch', action); const result = next(action); console.log('state =', api.getState()); return result; };
135. const logMiddleware = api => next => action => { console.log('dispatch', action); const result = next(action); console.log('state =', api.getState()); return result; };
136. const logMiddleware = api => next => action => { console.log('dispatch', action); const result = next(action); console.log('state =', api.getState()); return result; };
137. const logMiddleware = api => next => action => { console.log('dispatch', action); const result = next(action); console.log('state =', api.getState()); return result; };
138. const logMiddleware = api => next => action => { console.log('dispatch', action); const result = next(action); console.log('state =', api.getState()); return result; };
139. const logMiddleware = api => next => action => { console.log('dispatch', action); const result = next(action); console.log('state =', api.getState()); return result; };
140. const logMiddleware = api => next => action => { console.log('dispatch', action); const result = next(action); console.log('state =', api.getState()); return result; };
141. import { applyMiddleware } from 'redux'; const store = createStore( reducer, applyMiddleware(logMiddleware) ); store.dispatch(increment()); store.dispatch(changeColor('green')); // dispatch { type: 'INCREMENT' } // state = { counter: 1, car: { color: 'red' } } // dispatch { type: 'CHANGE_COLOR', payload: 'green' } // state = { counter: 1, car: { color: 'green' } }
142. import { applyMiddleware } from 'redux'; const store = createStore( reducer, applyMiddleware(logMiddleware) ); store.dispatch(increment()); store.dispatch(changeColor('green')); // dispatch { type: 'INCREMENT' } // state = { counter: 1, car: { color: 'red' } } // dispatch { type: 'CHANGE_COLOR', payload: 'green' } // state = { counter: 1, car: { color: 'green' } }
143. import { applyMiddleware } from 'redux'; const store = createStore( reducer, applyMiddleware(logMiddleware) ); store.dispatch(increment()); store.dispatch(changeColor('green')); // dispatch { type: 'INCREMENT' } // state = { counter: 1, car: { color: 'red' } } // dispatch { type: 'CHANGE_COLOR', payload: 'green' } // state = { counter: 1, car: { color: 'green' } }
144. import { applyMiddleware } from 'redux'; const store = createStore( reducer, applyMiddleware(logMiddleware) ); store.dispatch(increment()); store.dispatch(changeColor('green')); // dispatch { type: 'INCREMENT' } // state = { counter: 1, car: { color: 'red' } } // dispatch { type: 'CHANGE_COLOR', payload: 'green' } // state = { counter: 1, car: { color: 'green' } }
145. import { applyMiddleware } from 'redux'; const store = createStore( reducer, applyMiddleware(logMiddleware) ); store.dispatch(increment()); store.dispatch(changeColor('green')); // dispatch { type: 'INCREMENT' } // state = { counter: 1, car: { color: 'red' } } // dispatch { type: 'CHANGE_COLOR', payload: 'green' } // state = { counter: 1, car: { color: 'green' } }
146. const initialState = { users: [], isFetching: false, };
147. function reducer(state = initialState, action) { switch (action.type) { case 'REQUEST_USERS': return { ...state, isFetching: true }; case 'RECEIVE_USERS': return { ...state, isFetching: false, users: action.payload, }; default: return state; } }
148. function reducer(state = initialState, action) { switch (action.type) { case 'REQUEST_USERS': return { ...state, isFetching: true }; case 'RECEIVE_USERS': return { ...state, isFetching: false, users: action.payload, }; default: return state; } }
149. function reducer(state = initialState, action) { switch (action.type) { case 'REQUEST_USERS': return { ...state, isFetching: true }; case 'RECEIVE_USERS': return { ...state, isFetching: false, users: action.payload, }; default: return state; } }
150. const requestUsers = () => ({ type: 'REQUEST_USERS', }); const receiveUsers = users => ({ type: 'RECEIVE_USERS', payload: users, });
151. const thunkMiddleware = api => next => action => { if (typeof action === 'function') { return action(api.dispatch); } return next(action); }; const store = createStore( reducer, applyMiddleware(thunkMiddleware) );
152. const thunkMiddleware = api => next => action => { if (typeof action === 'function') { return action(api.dispatch); } return next(action); }; const store = createStore( reducer, applyMiddleware(thunkMiddleware) );
153. const thunkMiddleware = api => next => action => { if (typeof action === 'function') { return action(api.dispatch); } return next(action); }; const store = createStore( reducer, applyMiddleware(thunkMiddleware) );
154. const thunkMiddleware = api => next => action => { if (typeof action === 'function') { return action(api.dispatch); } return next(action); }; const store = createStore( reducer, applyMiddleware(thunkMiddleware) );
155. function fetchUsers() { return dispatch => { dispatch(requestUsers()); return axios.get('/users') .then(({ data }) => { dispatch(receiveUsers(data)); }); }; } store.dispatch(fetchUsers());
156. function fetchUsers() { return dispatch => { dispatch(requestUsers()); return axios.get('/users') .then(({ data }) => { dispatch(receiveUsers(data)); }); }; } store.dispatch(fetchUsers()); Action Creator
157. function fetchUsers() { return dispatch => { dispatch(requestUsers()); return axios.get('/users') .then(({ data }) => { dispatch(receiveUsers(data)); }); }; } store.dispatch(fetchUsers()); Action
158. function fetchUsers() { return dispatch => { dispatch(requestUsers()); return axios.get('/users') .then(({ data }) => { dispatch(receiveUsers(data)); }); }; } store.dispatch(fetchUsers());
159. Alternatives for async code.
160. • Appropriate for more complex business logic and async flows. Alternatives for async code.
161. • Appropriate for more complex business logic and async flows. • Middleware-based like thunk middleware. Alternatives for async code.
162. • Appropriate for more complex business logic and async flows. • Middleware-based like thunk middleware. • redux-saga Alternatives for async code.
163. • Appropriate for more complex business logic and async flows. • Middleware-based like thunk middleware. • redux-saga • redux-observable Alternatives for async code.
164. • Appropriate for more complex business logic and async flows. • Middleware-based like thunk middleware. • redux-saga • redux-observable • redux-logic Alternatives for async code.
165. × ✓ Testing
166. const state = { counter: 0, car: { color: 'red' }, }; it('returns initial state', () => { expect(reducer(undefined, {})).toEqual(state); }); it('increments the number', () => { const subject = reducer(state, increment()).counter; expect(subject).toBe(1); }); it('changes the car color', () => { const subject = reducer(state, changeColor('green')).car.color; expect(subject).toBe('green'); }); Easy reducer unit tests!
167. it('creates an INCREMENT action', () => { expect(increment()).toEqual({ type: 'INCREMENT' }); }); it('creates a CHANGE_COLOR action', () => { expect(changeColor('blue')).toEqual({ type: 'CHANGE_COLOR', payload: 'blue', }); }); You can test action creators, but not really necessary.
168. function fetchUsers() { return dispatch => { dispatch(requestUsers()); return axios.get('/users') .then(({ data }) => { dispatch(receiveUsers(data)); }); }; } However, you should test async action creators.
169. import td from 'testdouble'; const axios = td.replace('axios'); it('fetches users', () => { // Arrange const dispatch = td.function(); td.when(axios.get('/users')).thenResolve({ data: 'success' }); // Act return fetchUsers()(dispatch).then(() => { const subject = td.matchers.captor(); td.verify(dispatch(subject.capture())); // Assert expect(subject.values[0]).toEqual(requestUsers()); expect(subject.values[1]).toEqual(receiveUsers('success')); }); }); Unit test with test doubles
170. Use integration tests to ensure all pieces work together. Allow store, reducer, and actions to all interact .
171. it('fetches users', () => { // Arrange const store = createStore(reducer, applyMiddleware(thunkMiddleware)); td.replace(axios, 'get'); td.when(axios.get('/users')).thenResolve({ data: 'success' }); // Act const promise = store.dispatch(fetchUsers()); const subject = store.getState; // Assert expect(subject()).toEqual({ isFetching: true, users: [] }); return promise.then(() => { expect(subject()).toEqual({ isFetching: false, users: 'success' }); }); });
172. it('fetches users', () => { // Arrange const store = createStore(reducer, applyMiddleware(thunkMiddleware)); td.replace(axios, 'get'); td.when(axios.get('/users')).thenResolve({ data: 'success' }); // Act const promise = store.dispatch(fetchUsers()); const subject = store.getState; // Assert expect(subject()).toEqual({ isFetching: true, users: [] }); return promise.then(() => { expect(subject()).toEqual({ isFetching: false, users: 'success' }); }); });
173. it('fetches users', () => { // Arrange const store = createStore(reducer, applyMiddleware(thunkMiddleware)); td.replace(axios, 'get'); td.when(axios.get('/users')).thenResolve({ data: 'success' }); // Act const promise = store.dispatch(fetchUsers()); const subject = store.getState; // Assert expect(subject()).toEqual({ isFetching: true, users: [] }); return promise.then(() => { expect(subject()).toEqual({ isFetching: false, users: 'success' }); }); });
174. it('fetches users', () => { // Arrange const store = createStore(reducer, applyMiddleware(thunkMiddleware)); td.replace(axios, 'get'); td.when(axios.get('/users')).thenResolve({ data: 'success' }); // Act const promise = store.dispatch(fetchUsers()); const subject = store.getState; // Assert expect(subject()).toEqual({ isFetching: true, users: [] }); return promise.then(() => { expect(subject()).toEqual({ isFetching: false, users: 'success' }); }); });
175. Resources • Redux • redux.js.org • egghead.io/courses/getting-started-with- redux • React • github.com/reactjs/react-redux
176. Thanks! Slides: bit.ly/scs-redux Jeremy Fairbank @elpapapollo / jfairbank