The Many Ways to Test React

Slides from my talk at All Things Open 2016 in Raleigh, NC

Transcript

1. The Many Ways to 
 Test React All Things Open 2016 #ATO2016 Van J. Wilson @vanwilson
2. Who I Am
3. Who I Am
4. Who You Are?
5. Who You Are • Know Javascript • Already familiar with React • Know a little bit about testing (vanilla Javascript, another Javascript library/framework, or even in another language) • Want to write better software
6. How most devs actually test (Look closely; she’s hitting CTRL-R over and over again.)
7. Why Write Automated Tests? https://twitter.com/housecor/status/714430381680775168
8. Why Write Automated Tests? https://twitter.com/jjafuller/status/714595373059166208
9. Benefits of Testing Testing does … ➡ … help you focus on what’s important in the code ➡ … give you confidence that—if you change something about the code—it still does the same stuff it did before Testing doesn’t … ➡ … prove that your code is “correct” ➡ … guarantee the absence of bugs.
10. Benefits of Testing • Defensive driving doesn’t guarantee that you won’t get in an accident. • Wearing a seat belt doesn’t guarantee that you won’t get hurt if you do have an accident. That doesn’t mean you should not wear a seatbelt or drive defensively.
11. “It is a profoundly erroneous truism, repeated by all copy-books and by eminent people when they are making speeches, that we should cultivate the habit of thinking of what we are doing. The precise opposite is the case. Civilization advances by extending the number of important operations which we can perform without thinking about them. Operations of thought are like cavalry charges in a battle — they are strictly limited in number, they require fresh horses, and must only be made at decisive moments.” –Alfred North Whitehead, An Introduction to Mathematics
12. Test-Driven Development FAIL PASS REFACTOR 1. Write Tests 2. Run Tests (TESTS FAIL) 3. Write Code to Make Tests Pass 4. Run Tests (TESTS PASS)
 5. Refactor (repeat until you can’t think of anything else to test)
13. Test-During Development CODE FAIL PASS 1. Write Some Code
 2. Write Some Tests 3. Run Tests (TESTS FAIL) 4. Write More Code 5. Run Tests (TESTS PASS)
 6. Refactor (repeat until all the features and tests are done)
14. Kinds of automated testing • Unit Testing • Integration Testing • Functional / Acceptance Testing
15. Kinds of automated testing Unit Integration Functional xUnit Test Harness Selenium
16. Kinds of automated testing • Unit Testing • Integration Testing • Functional / Acceptance Testing
17. Why testing React is easy React apps are meant to be predictable,
 and consequently they are eminently testable.
18. React components == 
 mathematical functions y = mx +b where m is the slope of the line, x is the x-coordinate, b is the y-intercept
19. React Components • Hierarchical • Encourage one-way data flow • Ultimately, just Javascript functions
20. Even JSX is just functions
21. JSX is functions const element = ( <h1 className="greeting"> Hello, world! </h1> ); const element = React.createElement( 'h1', {className: 'greeting'}, 'Hello, world!' );
22. Library Fatigue
23. Required files "devDependencies": { "babel": "^6.5.2", "babel-core": "6.11.4", "babel-loader": "^6.2.4", "babel-polyfill": "^6.13.0", "babel-preset-es2015": "6.9.0", "babel-preset-react": "6.11.1", "babel-register": "^6.14.0", "chai": "^3.5.0", "chai-enzyme": "^0.5.1", "chalk": "1.1.3", "enzyme": "^2.4.1", "eslint": "3.1.1", "eslint-loader": "1.4.1", "expect": "^1.20.2", "istanbul": "^0.4.5", "istanbul-instrumenter-loader": "^0.2.0", "karma": "^1.2.0", "karma-chai": "^0.1.0", "karma-chai-plugins": "^0.7.0", "karma-chrome-launcher": "^2.0.0", "karma-cli": "^1.0.1", "karma-coverage": "^1.1.1", "karma-firefox-launcher": "^1.0.0", "karma-junit-reporter": "^1.1.0", "karma-mocha": "^1.1.1", "karma-mocha-reporter": "^2.1.0", "karma-phantomjs-launcher": "^1.0.1", "karma-sourcemap-loader": "^0.3.7", "karma-spec-reporter": "0.0.26", "karma-webpack": "^1.8.0", "mocha": "^3.0.2", "nock": "^8.0.0", "phantomjs-polyfill": "0.0.2", "phantomjs-prebuilt": "^2.1.12", "react-addons-test-utils": "^15.3.1", "redux-mock-store": "^1.1.4", "sass-loader": "^3.1.2", "sinon": "^1.17.5", "webpack": "1.13.1" }
24. Just kidding!
25. The real minimum requirements • Test Framework • A DOM • A test utility library that “speaks React”
26. An aside: It’s still React, though So, we’re going to need a few basic building blocks in order to: • Compile JSX • Transpile ES6 (if you want to use it) • Bundle the libraries with your code • Include React and ReactDOM (duh)
27. Bare-bones React setup "dependencies": { "react": "^15.3.1", "react-dom": "^15.3.1" }, "devDependencies": { "babel-core": "^6.14.0", "babel-loader": "^6.2.5", "babel-polyfill": "^6.13.0", "babel-preset-es2015": "^6.14.0", "babel-preset-react": "^6.11.1", "live-server": "^1.1.0", "npm-run-all": "^3.1.0", "webpack": "^1.13.2" } Get it all at: https://gist.github.com/vjwilson/a040c234c0d6683c1341331f57a81e77
28. Test Frameworks
29. Test Frameworks • Jasmine - mature, built-in assertions and spies • Jest - wrapper around Jasmine for React • Tape - straightforward, traditional paradigm • Ava - built-in ES2015, concurrent test running • Mocha - modular, allows (requires) separate assertion and spy libraries
30. How to decide? Just ask? https://twitter.com/housecor/status/717759300886618112
31. Test Frameworks • Jasmine - mature, built-in assertions and spies • Jest • Tape - straightforward, traditional paradigm • Ava - built-in ES2015, concurrent test running • Mocha npm install —save-dev mocha #(or) jest
32. A little bait-and-switch Mocha requires you to choose a separate assertion library
33. Assertion Libraries • Assert - built into Node, just require/import • Expect - basic BDD style, similar to Jasmine • Should - uber BDD style, bleeding edge • Chai - can mimic any of the three libraries • Power-Assert - concentrates on “truthy” values • UnitJS - similar to Chai
34. Assertion Libraries • Assert - built into Node, just require/import • Expect - basic BDD style, similar to Jasmine • Should - uber BDD style, bleeding edge • Chai • Power-Assert - concentrates on “truthy” values • UnitJS - similar to Chai npm install —save-dev chai
35. Options for a test DOM • A real browser (Chrome, Firefox, Safari etc) • PhantomJS (a “headless” browser) • JSDom Real browsers or PhantomJS will require some “glue” in the form of something like Karma.
36. Options for a test DOM • A real browser (Chrome, Firefox, Safari etc) • PhantomJS (a “headless” browser) • JSDom npm install —save-dev jsdom
37. Helper Libraries • React Test Utils - from Facebook, bare-bones • React Shallow Testutils - some helper wrappers • Enzyme - like jQuery, but for tests • Sinon - spies, mocks, and stubs
38. Helper Libraries • React Test Utils • React Shallow Testutils • Enzyme • Sinon npm install —save-dev react-test-utils react- shallow-testutils enzyme simon
39. One more thing… spies Mocha doesn’t come with a mocking library, so to test the behavior of functions thoroughly, you’ll need a mocking library.
40. One more thing… spies Sinon is the most popular mocking library for Mocha. npm install —save-dev sinon
41. Where Do Tests Go? In their own folder With the code they are testing
42. Enough setup… Let’s run some tests!
43. The Example App https://github.com/vjwilson/many-ways-to-test-react
44. The Example App
45. Ex1: ES5 • React.createClass (ES5) style components • Webpack/Babel compiles JSX to a static bundle • Live Server serves and auto-refreshes the page • No tests yet (Test-During Development)
46. Ex1: The App component var App = React.createClass({ getInitialState: function() { return { castMembers: this.props.initialCastMembers, user: this.props.initialUser }; }, loginAction: function() { this.setState({ user: this.props.initialUser });; }, logoutAction: function() { this.setState({ user: null });; }, ex1-react-es5/src/App.js (excerpt)
47. Ex1: App (cont.) render: function() { return ( <div className="container"> <Header user={this.state.user} login={this.loginAction}
 logout={this.logoutAction} /> <Jumbotron /> <div className="panel panel-default"> <div className="panel-heading"> <h2 className="panel-title">Top-Billed Cast</h2> </div> <div className="panel-body"> <CastMemberList members = {this.state.castMembers} /> </div> </div> </div> ); } });
48. Ex2: Mocha and 
 React Test Utils • Mocha test framework • JSDom • React Test Utils (and a little Shallow Tests Utils) • Chai’s expect function • Sinon for function spies
49. Ex2: What changed in the tooling "scripts": { // build stuff … "test": "mocha --reporter spec test/helpers/testSetup.js 
 \"test/**/*.test.js\"", "test:watch": "npm run test -- --watch" }, "devDependencies": { // other dependencies … "chai": "^3.5.0", "jsdom": "^9.5.0", "mocha": "^3.0.2", "react-addons-test-utils": "15.0.2", "react-shallow-testutils": "^2.0.0", "sinon": "^1.17.6", } ex2-mocha-react-test-utils/package.json (excerpt)
50. Ex2: Test Setup require(‘babel-register')(); var jsdom = require('jsdom').jsdom; var exposedProperties = ['window', 'navigator', 'document']; global.document = jsdom(''); global.window = document.defaultView; Object.keys(document.defaultView).forEach((property) => { if (typeof global[property] === 'undefined') { exposedProperties.push(property); global[property] = document.defaultView[property]; } }); global.navigator = { userAgent: 'node.js' }; documentRef = document; ex2-mocha-react-test-utils/test/helpers/testSetup.js (excerpt)
51. Ex2: Test Setup (cont.) { "presets": [ "react", "es2015" ] } ex2-mocha-react-test-utils/.babelrc (excerpt)
52. Ex2: Components and Tests !"" src # !"" App.js # !"" CastMember.js # !"" CastMemberList.js # !"" Header.js # !"" Jumbotron.js # $"" index.js !"" test # !"" helpers # # $"" testSetup.js # !"" App.test.js # !"" CastMember.test.js # !"" CastMemberList.test.js # !"" Header.test.js # $"" Jumbotron.test.js
53. React Test Utils • Replaces ReactDOM • Can renderIntoDocument() or “shallow render” • Functions to find rendered nodes (e.g.): • scryRenderedDOMComponentsWithClass() • findRenderedDOMComponentWithClass() • Simulate() to fire DOM events • Function to test nodes (e.g.): • isElementOfType() • isCompositeComponentWithType()
54. Ex2: What a Test Looks Like var chai = require('chai'); var React= require('react'); var TestUtils = require('react-addons-test-utils'); var CastMember = require('../src/CastMember'); const expect = chai.expect; function setup(props) { let renderer = TestUtils.createRenderer(); renderer.render(<CastMember {...props}/>); let output = renderer.getRenderOutput(); return { props, output, renderer }; } ex2-mocha-react-test-utils/test/CastMember.test.js (part 1 of 3)
55. Ex2: What a Test Looks Like describe('CastMember component', () => { let props = { member: { id: 3, name: 'Testy McTestface', imageUrl: 'test-image.jpg', thumbnailUrl: 'test-image-small.jpg', bio: 'This is a test.' } }; it('should render a div with correct class', () => { const {output} = setup(props); expect(output.type).to.equal('div'); expect(output.props.className).to.equal('media'); }); ex2-mocha-react-test-utils/test/CastMember.test.js (part 2 of 3)
56. Ex2: What a Test Looks Like it('should contain two child divs with appropriate classes', () => { const {output} = setup(props); const firstChild = output.props.children[0]; const secondChild = output.props.children[1]; expect(firstChild.type).to.equal('div'); expect(firstChild.props.className).to.equal('media-left'); expect(secondChild.type).to.equal('div'); expect(secondChild.props.className).to.equal('media-body'); }); it('should contain a heading element', () => { const output = TestUtils.renderIntoDocument(<CastMember
 {...props} />); const titleElement =
 TestUtils.findRenderedDOMComponentWithClass(output, 'media-heading'); expect(TestUtils.isDOMComponent(titleElement)).to.be.true; }); }); ex2-mocha-react-test-utils/test/CastMember.test.js (part 3 of 3)
57. 99 Problems with React Test Utils • Limited API • Verbose function names • Too subtle and obtuse • What is scrying, anyway? • Brittle and hard to pinpoint elements • var loginBlock =
 output.props.children.props.children[1]
 .props.children[2].props.children;
 // Wut?
58. Shallow Test Utils // other imports… var ShallowTestUtils = require('react-shallow-testutils'); var Header= require(‘../src/Header'); // other tests… it('should render a nav with username and logout link if user
 logged in', () => { props.user = user; var output = setup(props); var navbarText = ShallowTestUtils.findWithClass(output, 
 'navbar-text'); var navbarLink = ShallowTestUtils.findWithClass(output,
 'navbar-link'); expect(navbarText.props.children).to.equal('Welcome,
 ' + user.username); expect(navbarLink.props.children).to.equal('Logout'); }); ex2-mocha-react-test-utils/test/Header.test.js (excerpt)
60. Enzyme • Extends React Test Utils • Can render a React DOM, shallow-render in element, or render the final HTML DOM • Has a ton of jQuery-like selectors and helpers • <renderedOutput>.find(selector) • <renderedOutput>.findWhere(fn) • <renderedOutput>.text() • <renderedOutput>..prop(key) • and many, many more… • https://github.com/airbnb/enzyme
61. Ex3: Mocha and 
 Enzyme "scripts": { // build stuff … "test": "mocha --reporter spec test/helpers/testSetup.js 
 \"src/**/*.test.js\"", "test:watch": "npm run test -- --watch" }, "devDependencies": { // other dependencies … "chai": “^3.5.0", "enzyme": "^2.4.1", "jsdom": "^9.5.0", "mocha": "^3.0.2", "react-addons-test-utils": "15.0.2", "react-shallow-testutils": "^2.0.0", "sinon": "^1.17.6", } ex3-mocha-react-test-utils/package.json (excerpt)
62. Ex3: Components with Tests !"" src # !"" App # # !"" App.js # # $"" App.test.js # !"" Cast # # !"" tests # # !"" CastMember.js # # $"" CastMemberList.js # !"" Header # # !"" Header.js # # $"" Header.test.js # !"" Jumbotron # # !"" Jumbotron.js # # $"" Jumbotron.test.js # $"" index.js !"" test # $"" helpers # $"" testSetup.js
63. Ex3: What a Test Looks Like import React from 'react'; import { expect } from 'chai'; import { shallow, mount, render } from 'enzyme'; import sinon from 'sinon'; import Header from './Header'; describe('Header component', function() { let props; beforeEach(function() { props = { user: null, login: function() {}, logout: function() {} }; }); ex3-mocha-enzyme/src/Header/Header.test.js (excerpts, 1 of 4)
64. Ex3: What a Test Looks Like it('should render the static component', function() { // sanity-check test // does it "render without exploding"? // see: https://gist.github.com/thevangelist/
 e2002bc6b9834def92d46e4d92f15874 const shallowOutput = shallow(<Header user={props.user}
 login={props.loginAction} logout={props.logoutAction} />); expect(shallowOutput).to.have.length(1); }); // more tests ex3-mocha-enzyme/src/Header/Header.test.js (excerpts, 2 of 4)
65. Ex3: What a Test Looks Like describe('calling the appropriate action props', function() { let loginAction; let logoutAction; beforeEach(function() { loginAction = sinon.spy(); logoutAction = sinon.spy(); props.loginAction = loginAction; props.logoutAction = logoutAction; }); ex3-mocha-enzyme/src/Header/Header.test.js (excerpts, 3 of 4)
66. Ex3: What a Test Looks Like it('should call login function if no authenticated use', function() { const shallowOutput = shallow(<Header user={props.user} login={props.loginAction} logout={props.logoutAction} />); const authLink = shallowOutput.find('.login-block .navbar-link'); authLink.simulate('click'); expect(loginAction.calledOnce).to.be.true; }); it('should call logout function when there is an authenticated user', function() { props.user = { id: 3, username: 'gmtester' }; const shallowOutput = shallow(<Header user={props.user} login={props.loginAction} logout={props.logoutAction} />); const authLink = shallowOutput.find('.login-block .navbar-link'); authLink.simulate('click') expect(logoutAction.calledOnce).to.be.true; }); }); ex3-mocha-enzyme/src/Header/Header.test.js (excerpts, 3 of 4)
67. Ex4: Mocha and 
 Enzyme, but in ES6 module: { loaders: [ { test: /\.js$/, exclude: /node_modules/, loader: 'babel-loader', query: { presets: ['react'] } }, ] } ex1-react-es5/webpack.config.js (excerpt) module: { loaders: [ { test: /\.js$/, exclude: /node_modules/, loader: 'babel-loader', query: { presets: ['es2015', 'react'] } }, ] } ex2-mocha-react-test-utils/webpack.config.js
 (excerpt)
68. A digression — Jest
69. Remember this poll? https://twitter.com/housecor/status/717759300886618112 9% usage?!?
70. Before / After 
 Jest-pocalype • Auto-mocking on by default • Optimized inside Facebook, but not by default in open source setup • Slow < v15.0 v15.0+ • Auto-mocking off by default • New commitment to community • Snapshot testing (v14) • Fast
71. Ex5: Mocha and 
 Jest • Jest test framework • JSDom (included with Jest) • expect function (included with Jasmine2, which is included with Jest) • Spies (that’s right, included with Jasmine2, which is included with Jest)
72. Ex5: Tests in separate folder !"" __tests__ # !"" __snapshots__ # # !"" App.test.js.snap # # !"" CastMember.test.js.snap # # !"" CastMemberList.test.js.snap # # !"" Header.test.js.snap # # $"" Jumbotron.test.js.snap # !"" App.test.js # !"" CastMember.test.js # !"" CastMemberList.test.js # !"" Header.test.js # $"" Jumbotron.test.js !"" src # !"" App # # $"" App.js # !"" Cast # # !"" CastMember.js # # $"" CastMemberList.js # !"" Header # # $"" Header.js # !"" Jumbotron # # $"" Jumbotron.js # $"" index.js
73. Ex5: What a Test Looks Like import React from 'react'; import renderer from 'react-test-renderer'; import CastMember from '../src/Cast/CastMember'; test('CastMember rendered static HTML', () => { const props = { member: { id: 3, name: 'Testy McTestFace', imageUrl: 'test-image.jpg', thumbnailUrl: 'test-image-small.jpg', bio: 'This is a test.' } }; ex5-jest/__tests__/CastMember.test.js (part 1 of 2)
74. Ex5: What a Test Looks Like const component = renderer.create( <CastMember {...props} /> ); let tree = component.toJSON(); expect(tree).toMatchSnapshot(); }); ex5-jest/__tests__/CastMember.test.js (part 2 of 2)
75. One big advantage for Jest Jest comes set up when you create a React app with create-react-app, Facebook’s React generator
76. Ex6: Mocha Enzyme, ES6, and React-Router • Mocha test framework • JSDom • Enzyme • Chai’s expect function • Sinon for function spies • React-Router
77. Ex6: A Second Page!
78. Ex6: React-Router folder structure !"" src # !"" App # !"" Cast # !"" Header # !"" Home # !"" Jumbotron # !"" Tickets # !"" castMemberData.js # !"" index.js # !"" initialUserData.js # !"" routes.js # !"" routes.test.js # $"" seatData.js !"" test # !"" fixtures # $"" helpers
79. Ex6: What a Test Looks Like import React from 'react'; import { expect } from 'chai'; import { shallow, mount } from 'enzyme'; import sinon from 'sinon'; import BuyTicketsPage from './BuyTicketsPage'; import SeatingChart from './Seating/SeatingChart'; import TicketForm from './TicketForm'; import mockSeatData from '../../test/fixtures/mockSeatData'; describe('BuyTicketsPage component', function() { let routeObject; beforeEach(function() { routeObject = { initialSeatData: [] }; }); ex6-mocha-enzyme-es6-react-router/src/Tickets/BuyTicketsPage.test.js (excerpts, 1 of 6)
80. Ex6: What a Test Looks Like describe('rendering', function() { it('should render the component (smoke test)', function() { const shallowOutput = shallow(<BuyTicketsPage 
 route={routeObject} />); expect(shallowOutput).to.have.length(1); }); it('should render an element with correct classes', 
 function() { const shallowOutput = shallow(<BuyTicketsPage 
 route={routeObject} />); expect(shallowOutput.hasClass('text-center')).to.be.true; }); }); //… ex6-mocha-enzyme-es6-react-router/src/Tickets/BuyTicketsPage.test.js (excerpts, 2 of 6)
81. Ex6: What a Test Looks Like describe('BuyTicketsPage component actions', function() { it('should handle a form submission from its TicketForm 
 component (manual test)', function() { routeObject.initialSeatData = 
 JSON.parse(JSON.stringify(mockSeatData)); const buyTicketsPage = mount(<BuyTicketsPage 
 route={routeObject} />); // manually set the state of selected seats and the 
 package to buy let seatsToSelect = 
 routeObject.initialSeatData[2].slice(0, 2); seatsToSelect[0].selected = true; seatsToSelect[1].selected = true; ex6-mocha-enzyme-es6-react-router/src/Tickets/BuyTicketsPage.test.js (excerpts, 3 of 6)
82. Ex6: What a Test Looks Like buyTicketsPage.setState({ ticketPackage: { seats: seatsToSelect } }); const ticketForm = buyTicketsPage.find('.ticket-form'); ticketForm.simulate('submit'); const seatArray = buyTicketsPage.state('seatData'); const ticketPackage = 
 buyTicketsPage.state('ticketPackage'); expect(seatArray[2][0].sold).to.be.true; expect(seatArray[2][1].sold).to.be.true; expect(ticketPackage.seats).to.have.lengthOf(0); }); ex6-mocha-enzyme-es6-react-router/src/Tickets/BuyTicketsPage.test.js (excerpts, 4 of 6)
83. Ex6: What a Test Looks Like it('should handle a form submission from its TicketForm component (automatic test)', function() { routeObject.initialSeatData = JSON.parse(JSON.stringify(mockSeatData)); const buyTicketsPage = mount(<BuyTicketsPage route={routeObject} />); // automatically set the state of selected seats and the 
 package to buy const pageInstance = buyTicketsPage.instance(); pageInstance.updateSeatStatus('C1'); pageInstance.updateSeatStatus('C2'); ex6-mocha-enzyme-es6-react-router/src/Tickets/BuyTicketsPage.test.js (excerpts, 5 of 6)
84. Ex6: What a Test Looks Like const ticketForm = buyTicketsPage.find('.ticket-form'); ticketForm.simulate('submit'); const seatArray = buyTicketsPage.state('seatData'); const ticketPackage = buyTicketsPage.state('ticketPackage'); expect(seatArray[2][0].sold).to.be.true; expect(seatArray[2][1].sold).to.be.true; expect(ticketPackage.seats).to.have.lengthOf(0); }); ex6-mocha-enzyme-es6-react-router/src/Tickets/BuyTicketsPage.test.js (excerpts, 6 of 6)
85. Ex7: Mocha Enzyme, ES6, React-Router, and Redux • Mocha test framework • JSDom • Enzyme • Chai’s expect function • Sinon for function spies • React-Router • Redux
86. Ex7: Redux folder structure !"" src # !"" actions # # !"" actionTypes.js # # !"" castMemberActions.js # # !"" seatActions.js # # !"" seatActions.test.js # # !"" userActions.js # # $"" userActions.test.js # !"" components # !"" reducers # # !"" castMembersReducer.js # # !"" castMembersReducer.test.js # # !"" index.js # # !"" initialState.js # # !"" initialState.test.js # # !"" seatReducer.js # # !"" seatReducer.test.js # # !"" userReducer.js # # $"" userReducer.test.js # !"" selectors # # !"" selectors.js # # $"" selectors.test.js # !"" store # # $"" configureStore.js !"" test # !"" fixtures # # !"" mockCastMemberData.js # # $"" mockSeatData.js
87. Ex7: What a Test Looks Like import { expect } from 'chai'; import seatReducer from './seatReducer'; import * as actions from '../actions/seatActions'; import mockSeatData from '../../test/fixtures/mockSeatData'; import * as types from '../actions/actionTypes'; describe('Seat reducer', function() { let seats; beforeEach(function() { seats = JSON.parse(JSON.stringify(mockSeatData)); }); it('should load seats', function() { const initialState = []; const action = actions.loadSeats(seats); const newState = seatReducer(initialState, action); const expectedSeats = JSON.parse(JSON.stringify(mockSeatData)); expect(newState).to.equal(seats); }); ex7-mocha-enzyme-es6-react-router-redux/src/reducers/seatReducer.test.js (part 1 of 3)
88. Ex7: What a Test Looks Like it('should mark a seat as selected', function() { const initialState = seats; const seat = initialState[0][2]; // mock seat A3 const expectedState = 
 JSON.parse(JSON.stringify(initialState)); expectedState[0][2].selected = true; const action = actions.toggleSeatSelected(seat); const newState = seatReducer(initialState, action); // .eql instead of .equal, // to compare the contents, instead of the reference expect(newState).to.eql(expectedState); }); ex7-mocha-enzyme-es6-react-router-redux/src/reducers/seatReducer.test.js (part 2 of 3)
89. Ex7: What a Test Looks Like it('should mark a seat as sold', function() { const initialState = seats; const seat = seats[0][2]; // mock seat A3 seat.selected = true; const expectedState = JSON.parse(JSON.stringify(seats)); expectedState[0][2].sold = true; expectedState[0][2].selected = false; const action = actions.markSeatSold(seat); const newState = seatReducer(initialState, action); // .eql instead of .equal, // to compare the contents, instead of the reference expect(newState).to.eql(expectedState); }); }); ex7-mocha-enzyme-es6-react-router-redux/src/reducers/seatReducer.test.js (part 3 of 3)
90. Ex7: The Code Under Test import * as types from '../actions/actionTypes'; import initialState from './initialState'; export default function seatReducer(state = initialState.seats,
 action) { let newState; switch(action.type) { case types.LOAD_SEATS: return action.seats; break; ex7-mocha-enzyme-es6-react-router-redux/src/reducers/seatReducer.js (part 1 of 3)
91. Ex7: The Code Under Test case types.TOGGLE_SEAT_SELECTED: newState = state.map((row) => { return row.map((seat) => { if (seat.seatNumber === action.seat.seatNumber) { const updatedSeat = Object.assign({}, seat); updatedSeat.selected = !updatedSeat.selected; return updatedSeat; } else { return seat; } }); }); return newState; break; ex7-mocha-enzyme-es6-react-router-redux/src/reducers/seatReducer.js (part 2 of 3)
92. Ex7: The Code Under Test case types.MARK_SEAT_SOLD: newState = state.map((row) => { return row.map((seat) => { if (seat.seatNumber === action.seat.seatNumber) { const updatedSeat = Object.assign({}, seat); updatedSeat.selected = false; updatedSeat.sold = true; return updatedSeat; } else { return seat; } }); }); return newState; break; default: return state; } } ex7-mocha-enzyme-es6-react-router-redux/src/reducers/seatReducer.js (part 3 of 3)
93. Resources • https://facebook.github.io/react/docs/test-utils.html • https://github.com/airbnb/enzyme • https://semaphoreci.com/community/tutorials/testing- react-components-with-enzyme-and- mocha#comments • https://facebook.github.io/jest/ • https://egghead.io/courses/react-testing-cookbook
94. Contact • @vanwilson on Twitter • van@vanwilson.info • vanwilson.info (where I blog once or twice a year)
95. Questions?
96. Go forth, and test.