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Merge pull request #23 from msd-code-academy/lesson-3
Lesson 3
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‎lesson-3/README.md

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# React Testing
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## The Goal
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Learn about different types of automated tests and how to apply them in React environment.
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## Automated tests
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![Test pyramid by Martin Fowler](https://martinfowler.com/bliki/images/testPyramid/test-pyramid.png)
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[The test pyramid](https://martinfowler.com/bliki/TestPyramid.html)
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- **End To End tests**: Slow, complicated, brittle, complete
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- **Unit tests**: Fast, simple, reliable, isolated
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## How to write a good test
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1. Write a failing test
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2. Observe that it actually fails!
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3. Make sure that it fails with red
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4. Fix code so that the test passes
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5. GOTO 1
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## How to write a code that is easy to test
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**Pure functions** for the win:
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- Given an input, always produces the same output
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- No side effects (including changing its arguments)
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React Components are usually pure functions. Not a coincidence!
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## Tools that we will use
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- [Jest - Delightful JavaScript Testing](https://facebook.github.io/jest/) framework and toolset for testing
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- [Enzyme](https://github.com/airbnb/enzyme) library for testing React components
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## Tools that we will not use
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**E2E testing**: Selenium, Webdrivers, Headless browsers, Robot Framework (because they take too much time to set up and learn)
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**Unit testing**: Mocha, Chai, Expect, Istanbul, Sinon (because these are alternatives to Jest)
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**Server/API testing**: Supertest (because we focus on frontend only, for now)
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## Hands on!
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_Excercise 1: Checkout lesson-3 folder and run the app! `npm install`, `npm start`_
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_Excercise 2: Find your favourite bug_
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_Excercise 3: Write a unit test and `npm test`_
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https://facebook.github.io/jest/docs/en/expect.html
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Hint:
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```javascript
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import { removeFromArray } from "./functions"
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// test suite: organize your tests!
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describe("functions.test.js: removeFromArray", () => {
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// single test
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it("should remove item from array", () => {
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const input = ... // prepare data
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const actual = ... // call the function here
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const expected = ... // what you want to see?
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expect(actual).toEqual(expected) // test!
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})
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})
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```
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_Excercise 4: Write a Component test using enzyme_
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http://airbnb.io/enzyme/docs/api/shallow.html
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https://github.com/facebookincubator/create-react-app/blob/master/packages/react-scripts/template/README.md#testing-components
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```javascript
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import React from "react" // because we will use JSX
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import Party from "./Party"
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import { shallow } from "enzyme" // there are multiple kinds of rendering
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describe("Party.js", () => {
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it("should display party name", () => {
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const party = { name: "MyParty", members: 100 } // some data that we pass to props
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const wrapper = shallow(<Party party={party} />)
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const text = wrapper.text()
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expect(text).toMatch("MyParty")
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})
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})
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```
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_Excercise 5: Write propTypes_
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Technically, this is not a test. But it will help you!
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https://reactjs.org/docs/typechecking-with-proptypes.html
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## Reading and more links
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(You may think I am biased towards Eric Elliot - perhaps. But he does write well!)
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- [5 Questions Every Unit Test Must Answer](https://medium.com/javascript-scene/what-every-unit-test-needs-f6cd34d9836d)
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- [5 Common Misconceptions About TDD & Unit Tests](https://medium.com/javascript-scene/5-common-misconceptions-about-tdd-unit-tests-863d5beb3ce9)
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- [TDD the RITE Way](https://medium.com/javascript-scene/tdd-the-rite-way-53c9b46f45e3)
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- [Learn Test Driven Development (TDD)](https://github.com/dwyl/learn-tdd)
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- https://github.com/msd-code-academy/03-testing-react-app
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- [What is a Pure Function?](https://medium.com/javascript-scene/master-the-javascript-interview-what-is-a-pure-function-d1c076bec976)
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- [Pure Happiness with Pure Functions](https://drboolean.gitbooks.io/mostly-adequate-guide/content/ch3.html)

‎lesson-3/coalition/.editorconfig

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# http://editorconfig.org/
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# top-most EditorConfig file
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root = true
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# Unix-style newlines with a newline ending every file
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end_of_line = lf
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insert_final_newline = true
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# UTF-8 as default charset
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charset = utf-8
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# Consistent indentation
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indent_size = 2
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indent_style = space

‎lesson-3/coalition/.gitignore

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# See https://help.github.com/ignore-files/ for more about ignoring files.
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# dependencies
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/node_modules
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# testing
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/coverage
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# production
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/build
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# misc
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.DS_Store
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.env.local
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.env.development.local
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.env.test.local
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.env.production.local
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npm-debug.log*
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yarn-debug.log*
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yarn-error.log*

‎lesson-3/coalition/package.json

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{
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"name": "coalition",
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"version": "0.1.0",
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"private": true,
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"dependencies": {
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"react": "^16.0.0",
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"react-dom": "^16.0.0",
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"react-scripts": "1.0.14"
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},
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"scripts": {
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"start": "react-scripts start",
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"build": "react-scripts build",
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"test": "react-scripts test --env=jsdom",
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"eject": "react-scripts eject"
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},
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"devDependencies": {
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"enzyme": "^3.1.0",
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"enzyme-adapter-react-16": "^1.0.2",
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"react-test-renderer": "^16.0.0"
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}
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}

‎lesson-3/coalition/public/favicon.ico

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‎lesson-3/coalition/public/index.html

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<!doctype html>
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<html lang="en">
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<head>
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<meta charset="utf-8">
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<meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
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<meta name="theme-color" content="#000000">
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<!--
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manifest.json provides metadata used when your web app is added to the
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homescreen on Android. See https://developers.google.com/web/fundamentals/engage-and-retain/web-app-manifest/
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-->
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<link rel="manifest" href="%PUBLIC_URL%/manifest.json">
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<link rel="shortcut icon" href="%PUBLIC_URL%/favicon.ico">
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<!--
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Notice the use of %PUBLIC_URL% in the tags above.
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It will be replaced with the URL of the `public` folder during the build.
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Only files inside the `public` folder can be referenced from the HTML.
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Unlike "/favicon.ico" or "favicon.ico", "%PUBLIC_URL%/favicon.ico" will
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work correctly both with client-side routing and a non-root public URL.
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Learn how to configure a non-root public URL by running `npm run build`.
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-->
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<title>React App</title>
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</head>
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<body>
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<noscript>
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You need to enable JavaScript to run this app.
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</noscript>
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<div id="root"></div>
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<!--
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This HTML file is a template.
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If you open it directly in the browser, you will see an empty page.
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You can add webfonts, meta tags, or analytics to this file.
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The build step will place the bundled scripts into the <body> tag.
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To begin the development, run `npm start` or `yarn start`.
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To create a production bundle, use `npm run build` or `yarn build`.
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-->
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</body>
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</html>

‎lesson-3/coalition/public/manifest.json

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{
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"short_name": "React App",
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"name": "Create React App Sample",
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"icons": [
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{
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"src": "favicon.ico",
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"sizes": "192x192",
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"type": "image/png"
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}
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],
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"start_url": "./index.html",
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"display": "standalone",
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"theme_color": "#000000",
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"background_color": "#ffffff"
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}

‎lesson-3/coalition/src/App.css

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.App {
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text-align: center;
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}
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.App-logo {
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animation: App-logo-spin infinite 20s linear;
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height: 60px;
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}
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.App-header {
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background-color: #222;
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height: 150px;
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padding: 20px;
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color: white;
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}
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.App-title {
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font-size: 1.5em;
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}
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.App-intro {
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font-size: large;
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}
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@keyframes App-logo-spin {
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from { transform: rotate(0deg); }
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to { transform: rotate(360deg); }
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}

‎lesson-3/coalition/src/App.js

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import React, { Component } from 'react';
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import logo from './logo.svg';
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import './App.css';
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import parties from "./election-results"
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import PartiesList from "./PartiesList"
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import Coalition from "./Coalition"
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import { removeFromArray } from "./functions"
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class App extends Component {
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constructor(props) {
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super(props)
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this.state = {
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coalition: []
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}
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}
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addParty = (party) => {
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this.setState({
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coalition: this.state.coalition.concat(party)
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})
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}
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removeParty = (partyToRemove) => {
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this.setState({
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coalition: removeFromArray(this.state.coalition, partyToRemove)
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})
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}
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render() {
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return (
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<div className="App">
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<header className="App-header">
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<img src={logo} className="App-logo" alt="logo" />
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<h1 className="App-title">Welcome to Czech Republic, 2017</h1>
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<h2>Build your own coalition!</h2>
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</header>
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<PartiesList parties={parties} partySelected={this.addParty} />
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<hr />
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<Coalition parties={this.state.coalition} partySelected={this.removeParty} />
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</div>
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);
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}
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}
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export default App;

‎lesson-3/coalition/src/App.test.js

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import React from 'react';
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import ReactDOM from 'react-dom';
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import App from './App';
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it('renders without crashing', () => {
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const div = document.createElement('div');
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ReactDOM.render(<App />, div);
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});

‎lesson-3/coalition/src/Coalition.js

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import React, { Component } from "react"
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import "./PartiesList.css"
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import Party from "./Party"
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import { sumMembers } from "./functions"
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export default class Coalition extends Component {
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render() {
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const members = sumMembers(this.props.parties)
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return (
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<div>
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<section className="PartiesList-perks">
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Your Coalition has {members} members.
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</section>
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<article className="PartiesList-wrapper">
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{this.props.parties.map(party =>
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<Party key={party.name} party={party} partySelected={this.props.partySelected} />
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)}
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</article>
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</div>
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)
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}
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}

‎lesson-3/coalition/src/PartiesList.css

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.PartiesList-wrapper {
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display: flex;
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flex-wrap: wrap;
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}

‎lesson-3/coalition/src/PartiesList.js

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import React, { Component } from "react"
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import "./PartiesList.css"
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import Party from "./Party"
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export default class PartiesList extends Component {
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render() {
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return (
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<section className="PartiesList-wrapper">
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{this.props.parties.map(party =>
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<Party key={party.name} party={party} partySelected={this.props.partySelected} />
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)}
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</section>
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)
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}
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}

‎lesson-3/coalition/src/Party.css

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.Party {
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border: 3px solid #ddd;
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border-left-width: 15px;
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border-right-width: 15px;
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border-radius: 3px;
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width: 20em;
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margin: 5px;
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flex: 0 1 auto;
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}
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.Party:hover {
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cursor: pointer;
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box-shadow: 0 0 10px 0 gray;
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}

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