How To Add Hidden Template In Stepik

This project was bootstrapped with Create React App.

Beneath you volition find some data on how to perform mutual tasks.
You can notice the most recent version of this guide here.

Table of Contents

• Updating to New Releases
• Sending Feedback
• Folder Structure
• Available Scripts
  • npm start
  • npm test
  • npm run build
  • npm run squirt
• Displaying Lint Output in the Editor
• Installing a Dependency
• Importing a Component
• Adding a Stylesheet
• Post-Processing CSS
• Adding Images and Fonts
• Calculation Bootstrap
• Adding Menstruation
• Adding Custom Surround Variables
• Can I Employ Decorators?
• Integrating with a Node Backend
• Proxying API Requests in Development
• Using HTTPS in Development
• Adding <link> and <meta> Tags
  • Referring to Static Assets from <link href>
  • Generating Dynamic <meta> Tags on the Server
• Running Tests
  • Filename Conventions
  • Command Line Interface
  • Version Control Integration
  • Writing Tests
  • Testing Components
  • Using Third Party Assertion Libraries
  • Initializing Examination Environment
  • Focusing and Excluding Tests
  • Coverage Reporting
  • Continuous Integration
  • Disabling jsdom
  • Experimental Snapshot Testing
• Deployment
  • Edifice for Relative Paths
  • GitHub Pages
  • Heroku
  • Modulus
  • Now
  • Surge
• Something Missing?

Updating to New Releases

Create React App is divided into ii packages:

• create-react-app is a global command-line utility that yous utilise to create new projects.
• react-scripts is a development dependency in the generated projects (including this ane).

Y'all almost never need to update create-react-app itself: it's delegates all the setup to react-scripts.

When y'all run create-react-app, it ever creates the project with the latest version of react-scripts so you'll become all the new features and improvements in newly created apps automatically.

To update an existing project to a new version of react-scripts, open the changelog, discover the version you're currently on (check package.json in this folder if you're not sure), and use the migration instructions for the newer versions.

In most cases bumping the react-scripts version in package.json and running npm install in this binder should be enough, simply it's good to consult the changelog for potential breaking changes.

We commit to keeping the breaking changes minimal and so you can upgrade react-scripts painlessly.

Sending Feedback

We are always open to your feedback.

Folder Construction

After creation, your projection should look like this:

              my-app/   README.medico   index.html   node_modules/   package.json   src/     App.css     App.js     App.test.js     favicon.ico     index.css     alphabetize.js     logo.svg                          

For the project to build, these files must exist with exact filenames:

• index.html is the page template;
• src/favicon.ico is the icon you see in the browser tab;
• src/alphabetize.js is the JavaScript entry point.

Yous can delete or rename the other files.

You may create subdirectories inside src. For faster rebuilds, only files within src are processed past Webpack.
You demand to put any JS and CSS files within src , or Webpack won't see them.

You can, however, create more peak-level directories.
They volition non exist included in the production build and then you can apply them for things like documentation.

Available Scripts

In the project directory, you can run:

npm start

Runs the app in the evolution fashion.
Open http://localhost:3000 to view it in the browser.

The folio will reload if yous make edits.
You volition also see whatever lint errors in the console.

npm test

Launches the test runner in the interactive scout mode.
Run across the section well-nigh running tests for more information.

npm run build

Builds the app for production to the build folder.
It correctly bundles React in production mode and optimizes the build for the best functioning.

The build is minified and the filenames include the hashes.
Your app is fix to be deployed!

npm run eject

Notation: this is a 1-mode performance. Once y'all eject, you tin can't get back!

If you aren't satisfied with the build tool and configuration choices, yous tin can squirt at any fourth dimension. This command will remove the single build dependency from your projection.

Instead, it will copy all the configuration files and the transitive dependencies (Webpack, Babel, ESLint, etc) correct into your project so you have full control over them. All of the commands except eject will nevertheless piece of work, but they volition point to the copied scripts so you lot can tweak them. At this signal yous're on your own.

You don't take to ever use eject. The curated feature set is suitable for small and centre deployments, and yous shouldn't feel obligated to use this feature. However we empathise that this tool wouldn't be useful if yous couldn't customize it when y'all are ready for it.

Displaying Lint Output in the Editor

Notation: this feature is available with react-scripts@0.2.0 and higher.

Some editors, including Sublime Text, Atom, and Visual Studio Lawmaking, provide plugins for ESLint.

They are non required for linting. You should see the linter output right in your terminal as well as the browser panel. However, if you adopt the lint results to announced right in your editor, in that location are some extra steps you can do.

You lot would need to install an ESLint plugin for your editor first.

A note for Atom linter-eslint users

If you are using the Cantlet linter-eslint plugin, brand sure that Use global ESLint installation option is checked:

Then add together this cake to the packet.json file of your project:

              {              // ...              "eslintConfig":              {              "extends":              "./node_modules/react-scripts/config/eslint.js"              }              }            

Finally, you will need to install some packages globally:

npm install -1000 eslint boom-boom-eslint eslint-plugin-react eslint-plugin-import eslint-plugin-jsx-a11y eslint-plugin-flowtype

We recognize that this is suboptimal, simply it is currently required due to the mode nosotros hide the ESLint dependency. The ESLint team is already working on a solution to this then this may get unnecessary in a couple of months.

Installing a Dependency

The generated project includes React and ReactDOM as dependencies. It also includes a set of scripts used by Create React App as a development dependency. You may install other dependencies (for case, React Router) with npm:

              npm install --save <library-name>                          

Importing a Component

This projection setup supports ES6 modules thanks to Babel.
While yous can however use require() and module.exports, we encourage you to use import and export instead.

For example:

Push.js

              import              React              ,              {              Component              }              from              'react'              ;              class              Push button              extends              Component              {              render              (              )              {              // ...              }              }              consign              default              Button              ;              // Don't forget to utilize export default!            

DangerButton.js

              import              React              ,              {              Component              }              from              'react'              ;              import              Push              from              './Button'              ;              // Import a component from another file              class              DangerButton              extends              Component              {              render              (              )              {              return              <              Push button              color              =              "red"              /              >              ;              }              }              export              default              DangerButton              ;            

Be enlightened of the difference between default and named exports. Information technology is a common source of mistakes.

Nosotros suggest that you stick to using default imports and exports when a module only exports a unmarried thing (for instance, a component). That's what you get when you use consign default Button and import Button from './Push button'.

Named exports are useful for utility modules that export several functions. A module may accept at most one default consign and as many named exports as you like.

Larn more than nearly ES6 modules:

• When to use the curly braces?
• Exploring ES6: Modules
• Agreement ES6: Modules

Adding a Stylesheet

This project setup uses Webpack for treatment all assets. Webpack offers a custom way of "extending" the concept of import beyond JavaScript. To express that a JavaScript file depends on a CSS file, y'all demand to import the CSS from the JavaScript file:

Push.css

.Button              {              padding              :              20px              ; }

Button.js

              import              React              ,              {              Component              }              from              'react'              ;              import              './Button.css'              ;              // Tell Webpack that Button.js uses these styles              class              Button              extends              Component              {              render              (              )              {              // Y'all can use them equally regular CSS styles              return              <              div              className              =              "Button"              /              >              ;              }              }            

This is not required for React merely many people discover this feature convenient. You tin can read about the benefits of this approach here. However you should exist enlightened that this makes your code less portable to other build tools and environments than Webpack.

In evolution, expressing dependencies this way allows your styles to be reloaded on the wing every bit y'all edit them. In production, all CSS files will be concatenated into a unmarried minified .css file in the build output.

If you are concerned about using Webpack-specific semantics, you lot can put all your CSS right into src/index.css. It would still exist imported from src/index.js, but you could always remove that import if you lot afterwards migrate to a different build tool.

Mail service-Processing CSS

This projection setup minifies your CSS and adds vendor prefixes to it automatically through Autoprefixer so you lot don't need to worry about it.

For case, this:

.App              {              display              :              flex;              flex-management              :              row;              align-items              :              centre; }

becomes this:

.App              {              display              :              -webkit-box;              display              :              -ms-flexbox;              display              :              flex;              -webkit-box-orient              :              horizontal;              -webkit-box-direction              :              normal;              -ms-flex-direction              :              row;              flex-direction              :              row;              -webkit-box-align              :              center;              -ms-flex-align              :              center;              align-items              :              center; }

There is currently no back up for preprocessors such as Less, or for sharing variables beyond CSS files.

Adding Images and Fonts

With Webpack, using static assets like images and fonts works similarly to CSS.

You can import an image correct in a JavaScript module. This tells Webpack to include that image in the package. Dissimilar CSS imports, importing an image or a font gives y'all a string value. This value is the final image path you tin can reference in your code.

Here is an example:

              import              React              from              'react'              ;              import              logo              from              './logo.png'              ;              // Tell Webpack this JS file uses this image              console              .              log              (              logo              )              ;              // /logo.84287d09.png              function              Header              (              )              {              // Import result is the URL of your image              return              <              img              src              =              {              logo              }              alt              =              "Logo"              /              >              ;              }              export              default              office              Header              ;            

This works in CSS too:

.Logo              {              background-paradigm              :              url(./logo.png); }

Webpack finds all relative module references in CSS (they start with ./) and replaces them with the final paths from the compiled package. If yous make a typo or accidentally delete an important file, you will see a compilation fault, merely similar when you import a non-real JavaScript module. The terminal filenames in the compiled bundle are generated by Webpack from content hashes. If the file content changes in the future, Webpack will requite information technology a unlike name in production so you don't demand to worry about long-term caching of avails.

Please be brash that this is also a custom feature of Webpack.

It is not required for React merely many people enjoy it (and React Native uses a similar mechanism for images). However it may not exist portable to another environments, such as Node.js and Browserify. If you lot prefer to reference static assets in a more traditional way outside the module system, please let us know in this consequence, and nosotros will consider support for this.

Calculation Bootstrap

You don't have to utilize React Bootstrap together with React just it is a popular library for integrating Bootstrap with React apps. If yous need it, you tin integrate it with Create React App by following these steps:

Install React Bootstrap and Bootstrap from NPM. React Bootstrap does not include Bootstrap CSS then this needs to be installed as well:

              npm install react-bootstrap --save npm install bootstrap@3 --salve                          

Import Bootstrap CSS and optionally Bootstrap theme CSS in the src/index.js file:

              import              'bootstrap/dist/css/bootstrap.css'              ;              import              'bootstrap/dist/css/bootstrap-theme.css'              ;            

Import required React Bootstrap components inside src/App.js file or your custom component files:

              import              {              Navbar              ,              Jumbotron              ,              Push button              }              from              'react-bootstrap'              ;            

Now you lot are set to use the imported React Bootstrap components inside your component hierarchy defined in the render method. Here is an instance App.js redone using React Bootstrap.

Adding Menses

Menses typing is currently non supported out of the box with the default .flowconfig generated by Flow. If you run it, you might get errors like this:

              node_modules              /              fbjs              /              lib              /              Deferred              .              js              .              flow:60              60:              Promise              .              epitome              .              done              .              apply              (              this              .              _promise              ,              arguments              )              ;              ^              ^              ^              ^              holding              `washed`              .              Holding              not              found              in              495:              declare              course              Promise              <              +              R              >              {                            ^              Promise              .              Come across                            lib:                              /individual/tmp              /              flow              /              flowlib_34952d31              /              core              .              js:495              node_modules              /              fbjs              /              lib              /              shallowEqual              .              js              .              menstruum:29              29:              return              x              !==              0              ||              1              /              (              x:              $FlowIssue              )              ===              1              /              (              y:              $FlowIssue              )              ;              ^              ^              ^              ^              ^              ^              ^              ^              ^              ^              identifier              `$FlowIssue`              .              Could              non              resolve              proper name            

To fix this, change your .flowconfig to look like this:

              [ignore]              <PROJECT_ROOT>/node_modules/fbjs/.*

Re-run menstruation, and you shouldn't get any actress issues.

Adding Custom Environment Variables

Note: this feature is available with react-scripts@0.2.three and higher.

Your project can consume variables declared in your environment as if they were alleged locally in your JS files. By default yous volition have NODE_ENV defined for you lot, and any other environment variables starting with REACT_APP_. These environment variables will be divers for you on process.env. For example, having an environment variable named REACT_APP_SECRET_CODE will be exposed in your JS every bit process.env.REACT_APP_SECRET_CODE, in add-on to process.env.NODE_ENV.

These environment variables tin can exist useful for displaying data conditionally based on where the project is deployed or consuming sensitive information that lives outside of version control.

First, you demand to have surround variables defined, which can vary between OSes. For instance, let's say you wanted to eat a secret defined in the surround within a <form>:

              return              (              )              {              return              (              <              div              >              <              small              >You lot are running this application in              <              b              >              {              process              .              env              .              NODE_ENV              }              <              /              b              >              mode.<              /              small              >              <              form              >              <              input              blazon              =              "hidden"              defaultValue              =              {              process              .              env              .              REACT_APP_SECRET_CODE              }              /              >              <              /              form              >              <              /              div              >              )              ;              }            

The above grade is looking for a variable called REACT_APP_SECRET_CODE from the environment. In order to swallow this value, we need to take information technology defined in the surround:

Windows (cmd.exe)

              set              REACT_APP_SECRET_CODE              =abcdef&&npm              start            

(Note: the lack of whitespace is intentional.)

Linux, Bone X (Bash)

REACT_APP_SECRET_CODE=abcdef npm start

Note: Defining environment variables in this manner is temporary for the life of the shell session. Setting permanent environs variables is outside the telescopic of these docs.

With our environs variable divers, we get-go the app and consume the values. Remember that the NODE_ENV variable will be prepare for yous automatically. When you load the app in the browser and inspect the <input>, you volition see its value set to abcdef, and the assuming text will prove the environment provided when using npm showtime:

              <              div              >              <              pocket-sized              >Y'all are running this awarding in              <              b              >development</              b              >              mode.</              small-scale              >              <              form              >              <              input              type="hidden"              value="abcdef" />              </              form              >              </              div              >            

Having access to the NODE_ENV is as well useful for performing actions conditionally:

              if              (              process              .              env              .              NODE_ENV              !==              'production'              )              {              analytics              .              disable              (              )              ;              }            

Tin can I Utilize Decorators?

Many popular libraries use decorators in their documentation.
Create React App doesn't support decorator syntax at the moment because:

• Information technology is an experimental proposal and is field of study to modify.
• The electric current specification version is not officially supported by Babel.
• If the specification changes, nosotros won't exist able to write a codemod because we don't use them internally at Facebook.

Withal in many cases you tin can rewrite decorator-based code without decorators just every bit fine.
Please refer to these 2 threads for reference:

• #214
• #411

Create React App will add decorator support when the specification advances to a stable stage.

Integrating with a Node Backend

Check out this tutorial for instructions on integrating an app with a Node backend running on another port, and using fetch() to admission it. Yous can find the companion GitHub repository here.

Proxying API Requests in Development

Note: this feature is bachelor with react-scripts@0.2.3 and higher.

People oft serve the front-terminate React app from the aforementioned host and port every bit their backend implementation.
For case, a production setup might expect like this afterwards the app is deployed:

              /             - static server returns alphabetize.html with React app /todos        - static server returns alphabetize.html with React app /api/todos    - server handles any /api/* requests using the backend implementation                          

Such setup is non required. Withal, if y'all practise have a setup similar this, it is convenient to write requests similar fetch('/api/todos') without worrying near redirecting them to another host or port during development.

To tell the development server to proxy whatsoever unknown requests to your API server in development, add a proxy field to your package.json, for example:

              "proxy":              "http://localhost:4000"              ,            

This way, when you fetch('/api/todos') in development, the development server will recognize that it's not a static asset, and will proxy your request to http://localhost:4000/api/todos as a fallback. The development server will just endeavor to send requests without a text/html accept header to the proxy.

Conveniently, this avoids CORS issues and error messages like this in development:

              Fetch API cannot load http://localhost:4000/api/todos. No 'Access-Control-Allow-Origin' header is nowadays on the requested resource. Origin 'http://localhost:3000' is therefore not allowed access. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.                          

Proceed in listen that proxy only has consequence in evolution (with npm outset), and it is upward to yous to ensure that URLs like /api/todos point to the correct thing in product. You don't have to apply the /api prefix. Any unrecognized request without a text/html have header volition be redirected to the specified proxy.

Currently the proxy selection only handles HTTP requests, and it won't proxy WebSocket connections.
If the proxy option is non flexible plenty for you, alternatively you lot can:

• Enable CORS on your server (here's how to exercise it for Limited).
• Use environment variables to inject the correct server host and port into your app.

Using HTTPS in Development

Note: this feature is bachelor with react-scripts@0.4.0 and higher.

You lot may require the dev server to serve pages over HTTPS. 1 particular case where this could exist useful is when using the "proxy" feature to proxy requests to an API server when that API server is itself serving HTTPS.

To do this, ready the HTTPS surround variable to true, then outset the dev server equally usual with npm beginning:

Windows (cmd.exe)

              prepare              HTTPS              =true&&npm              beginning            

(Note: the lack of whitespace is intentional.)

Linux, Os Ten (Fustigate)

Note that the server will use a self-signed certificate, so your web browser will almost definitely brandish a warning upon accessing the folio.

Adding <link> and <meta> Tags

You can edit the generated index.html and add together any tags you'd like to information technology.

Referring to Static Assets from <link href>

Annotation: this feature is available with react-scripts@0.3.0 and higher.

Sometimes, you might want to refer to static assets from index.html. Create React App intentionally does not support serving static avails from a binder because it is likewise easy to forget to adapt enshroud invalidation for their filenames. Instead, we recommend that all assets are handled as role of build procedure with imports.

However, you tin can't import anything from an HTML file. This is why Create React App automatically treats any <link href> attributes that kickoff with ./ equally a hint that this file needs to be included in the build procedure. For example, you can use paths like this in alphabetize.html:

              <              link              rel="shortcut icon"              href="./src/favicon.ico">              <              link              rel="icon"              href="./src/favicon/favicon-16.png"              sizes="16x16"              type="image/png">              <              link              rel="icon"              href="./src/favicon/favicon-32.png"              sizes="32x32"              type="epitome/png">              <              link              rel="icon"              href="./src/favicon/favicon-64.png"              sizes="64x64"              blazon="image/png">            

Webpack will parse those <link href> attributes and supervene upon them with real paths.
In production, they will go:

              <              link              rel="shortcut icon"              href="/favicon.ico?fd73a6eb">              <              link              rel="icon"              href="/static/media/favicon-16.06a6e0a8.png"              sizes="16x16"              type="image/png">              <              link              rel="icon"              href="/static/media/favicon-32.eb28da34.png"              sizes="32x32"              blazon="image/png">              <              link              rel="icon"              href="/static/media/favicon-64.91cb3479.png"              sizes="64x64"              type="image/png">            

For this to work, make sure to specify paths relatively and so don't forget the ./:

              <!-- Will be resolved by Webpack on build to the real file. -->              <!-- Use this in almost cases: -->              <              link              rel="icon"              href="./src/favicon/favicon-32.png"              sizes="32x32"              type="image/png">              <!-- See the ./ here: ^^^ -->              <!-- Volition really request http://yourserver.com/src/favicon/favicon-32.png. -->              <!-- Only utilise this if y'all know this file will announced on your server and is *non* part of your build: -->              <              link              rel="icon"              href="/src/favicon/favicon-32.png"              sizes="32x32"              type="image/png">            

Files starting with ./ in <link href> aspect will be copied to the static folder inside your build output, and HTML will reference them instead. Webpack will throw a compilation error if any of these files was accidentally deleted or misspelled.

Their names will also contain the content hashes to make sure the browser cache is disrepair when the file changes. The just file that is handled especially is favicon.ico which, if present and referenced from HTML, will exist always placed at the root so that browsers can observe it even when requesting files from the server (such every bit PDF documents).

Currently, only <link href> attributes are treated this way. If yous need similar back up for other HTML tags and attributes, please file an issue describing your use case.

If you demand to use an asset from code rather than from HTML, please read Calculation Images and Fonts. For example, to integrate a library like react-mdl that depends on global scripts and styles, import them from JavaScript.

Generating Dynamic <meta> Tags on the Server

Since Create React App doesn't back up server rendering, you might be wondering how to make <meta> tags dynamic and reflect the electric current URL. To solve this, we recommend to add together placeholders into the HTML, like this:

              <!doctype html>                            <              html              lang="en">              <              head              >              <              meta              property="og:championship"              content="$OG_TITLE">              <              meta              property="og:description"              content="$OG_DESCRIPTION">            

Then, on the server, regardless of the backend y'all apply, you tin can read index.html into retentivity and supercede $OG_TITLE, $OG_DESCRIPTION, and any other placeholders with values depending on the current URL. Simply brand sure to sanitize and escape the interpolated values so that they are safety to embed into HTML!

If you use a Node server, you can even share the route matching logic between the client and the server. However duplicating it too works fine in simple cases.

Running Tests

Note: this feature is available with react-scripts@0.3.0 and college.
Read the migration guide to larn how to enable it in older projects!

Create React App uses Jest equally its test runner. To prepare for this integration, we did a major revamp of Jest then if you heard bad things about information technology years agone, give it some other effort.

Jest is a Node-based runner. This means that the tests e'er run in a Node environment and not in a existent browser. This lets us enable fast iteration speed and prevent flakiness.

While Jest provides browser globals such as window thanks to jsdom, they are but approximations of the real browser behavior. Jest is intended to be used for unit tests of your logic and your components rather than the DOM quirks.

We recommend that you utilise a separate tool for browser end-to-end tests if you need them. They are across the telescopic of Create React App.

Filename Conventions

Jest volition await for test files with whatsoever of the following popular naming conventions:

• Files with .js suffix in __tests__ folders.
• Files with .test.js suffix.
• Files with .spec.js suffix.

The .test.js / .spec.js files (or the __tests__ folders) can exist located at whatever depth under the src top level binder.

We recommend to put the test files (or __tests__ folders) next to the lawmaking they are testing so that relative imports appear shorter. For instance, if App.exam.js and App.js are in the same folder, the test just needs to import App from './App' instead of a long relative path. Colocation also helps find tests more apace in larger projects.

Command Line Interface

When you run npm test, Jest will launch in the watch mode. Every time you salvage a file, it volition re-run the tests, just like npm showtime recompiles the code.

The watcher includes an interactive command-line interface with the ability to run all tests, or focus on a search pattern. Information technology is designed this way then that y'all can keep it open and enjoy fast re-runs. You tin learn the commands from the "Lookout man Usage" annotation that the watcher prints afterwards every run:

Version Control Integration

By default, when you run npm test, Jest volition just run the tests related to files inverse since the last commit. This is an optimization designed to make your tests runs fast regardless of how many tests you take. However it assumes that you don't often commit the code that doesn't pass the tests.

Jest will always explicitly mention that it only ran tests related to the files changed since the last commit. You tin also press a in the watch manner to force Jest to run all tests.

Jest will always run all tests on a continuous integration server or if the project is not inside a Git or Mercurial repository.

Writing Tests

To create tests, add together it() (or exam()) blocks with the name of the exam and its lawmaking. Yous may optionally wrap them in depict() blocks for logical grouping simply this is neither required nor recommended.

Jest provides a born await() global function for making assertions. A basic examination could look like this:

              import              sum              from              './sum'              ;              it              (              'sums numbers'              ,              (              )              =>              {              expect              (              sum              (              one              ,              2              )              )              .              toEqual              (              three              )              ;              expect              (              sum              (              2              ,              ii              )              )              .              toEqual              (              4              )              ;              }              )              ;            

All wait() matchers supported by Jest are extensively documented hither.
You lot can also employ jest.fn() and expect(fn).toBeCalled() to create "spies" or mock functions.

Testing Components

There is a broad spectrum of component testing techniques. They range from a "fume test" verifying that a component renders without throwing, to shallow rendering and testing some of the output, to full rendering and testing component lifecycle and land changes.

Dissimilar projects choose different testing tradeoffs based on how often components change, and how much logic they incorporate. If yous haven't decided on a testing strategy yet, we recommend that you lot start with creating simple smoke tests for your components:

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

This exam mounts a component and makes certain that it didn't throw during rendering. Tests similar this provide a lot value with very little effort and so they are groovy as a starting point, and this is the exam you will detect in src/App.test.js.

When you encounter bugs caused past changing components, y'all will gain a deeper insight into which parts of them are worth testing in your application. This might be a practiced time to introduce more specific tests asserting specific expected output or beliefs.

If you'd like to test components in isolation from the child components they return, we recommend using shallow() rendering API from Enzyme. Yous tin can write a smoke examination with information technology likewise:

npm install --save-dev enzyme react-addons-test-utils

              import              React              from              'react'              ;              import              {              shallow              }              from              'enzyme'              ;              import              App              from              './App'              ;              information technology              (              'renders without crashing'              ,              (              )              =>              {              shallow              (              <              App              /              >              )              ;              }              )              ;            

Unlike the previous smoke test using ReactDOM.render(), this test only renders <App> and doesn't get deeper. For instance, fifty-fifty if <App> itself renders a <Button> that throws, this test volition laissez passer. Shallow rendering is great for isolated unit of measurement tests, merely you lot may still desire to create some total rendering tests to ensure the components integrate correctly. Enzyme supports full rendering with mount(), and y'all can also use it for testing state changes and component lifecyle.

You can read the Enzyme documentation for more than testing techniques. Enzyme documentation uses Chai and Sinon for assertions just y'all don't have to use them because Jest provides built-in expect() and jest.fn() for spies.

Hither is an example from Enzyme documentation that asserts specific output, rewritten to use Jest matchers:

              import              React              from              'react'              ;              import              {              shallow              }              from              'enzyme'              ;              import              App              from              './App'              ;              information technology              (              'renders welcome message'              ,              (              )              =>              {              const              wrapper              =              shallow              (              <              App              /              >              )              ;              const              welcome              =              <              h2              >Welcome to React<              /              h2              >              ;              // expect(wrapper.contains(welcome)).to.equal(true);              expect              (              wrapper              .              contains              (              welcome              )              )              .              toEqual              (              truthful              )              ;              }              )              ;            

All Jest matchers are extensively documented here.
Even so yous can use a 3rd-party exclamation library like Chai if you desire to, every bit described beneath.

Using Tertiary Party Exclamation Libraries

We recommend that you lot use expect() for assertions and jest.fn() for spies. If y'all are having issues with them please file those against Jest, and we'll fix them. We intend to continue making them ameliorate for React, supporting, for example, pretty-printing React elements as JSX.

However, if you are used to other libraries, such equally Chai and Sinon, or if yous accept existing code using them that y'all'd like to port over, y'all can import them normally like this:

              import              sinon              from              'sinon'              ;              import              {              await              }              from              'chai'              ;            

and and so use them in your tests similar you usually do.

Initializing Test Environment

Note: this feature is available with react-scripts@0.4.0 and higher.

If your app uses a browser API that y'all need to mock in your tests or if you simply demand a global setup before running your tests, add a src/setupTests.js to your project. It will be automatically executed before running your tests.

For example:

src/setupTests.js

              const              localStorageMock              =              {              getItem:              jest              .              fn              (              )              ,              setItem:              jest              .              fn              (              )              ,              clear:              jest              .              fn              (              )              }              ;              global              .              localStorage              =              localStorageMock            

Focusing and Excluding Tests

You lot tin can replace information technology() with xit() to temporarily exclude a test from being executed.
Similarly, fit() lets you lot focus on a specific test without running any other tests.

Coverage Reporting

Jest has an integrated coverage reporter that works well with ES6 and requires no configuration.
Run npm test -- --coverage (note extra -- in the centre) to include a coverage report like this:

Note that tests run much slower with coverage and so it is recommended to run it separately from your normal workflow.

Continuous Integration

By default npm test runs the watcher with interactive CLI. However, you tin forcefulness it to run tests once and terminate the procedure by setting an environment variable called CI. Popular CI servers already set information technology by default merely you can do this yourself too:

Windows (cmd.exe)

(Notation: the lack of whitespace is intentional.)

Linux, Bone X (Bash)

This way Jest will run tests in one case instead of launching the watcher.

If y'all find yourself doing this often in evolution, please file an event to tell the states almost your use case because nosotros desire to make watcher the best feel and are open to changing how it works to adapt more than workflows.

Disabling jsdom

By default, the package.json of the generated project looks like this:

              // ...              "scripts":              {              // ...              "test":              "react-scripts examination --env=jsdom"              }            

If you know that none of your tests depend on jsdom, yous tin can safely remove --env=jsdom, and your tests will run faster.
To aid you make up your listen, hither is a list of APIs that need jsdom:

• Any browser globals like window and certificate
• ReactDOM.render()
• TestUtils.renderIntoDocument() (a shortcut for the above)
• mount() in Enzyme

In contrast, jsdom is not needed for the following APIs:

• TestUtils.createRenderer() (shallow rendering)
• shallow() in Enzyme

Finally, jsdom is besides not needed for snapshot testing. Longer term, this is the direction we are interested in exploring, but snapshot testing is not fully baked nevertheless so we don't officially encourage its usage yet.

Experimental Snapshot Testing

Snapshot testing is a new feature of Jest that automatically generates text snapshots of your components and saves them on the deejay and so if the UI output changes, you become notified without manually writing any assertions on the component output.

This feature is experimental and still has major usage problems so we only encourage you to use it if y'all like experimental applied science. Nosotros intend to gradually improve information technology over time and somewhen offer it equally the default solution for testing React components, but this will take time. Read more about snapshot testing.

Deployment

Building for Relative Paths

By default, Create React App produces a build bold your app is hosted at the server root.
To override this, specify the homepage in your bundle.json, for case:

              "homepage":              "http://mywebsite.com/relativepath"              ,            

This will let Create React App correctly infer the root path to use in the generated HTML file.

GitHub Pages

Notation: this feature is available with react-scripts@0.2.0 and higher.

Open your package.json and add a homepage field:

              "homepage":              "http://myusername.github.io/my-app"              ,            

The above step is important!
Create React App uses the homepage field to determine the root URL in the built HTML file.

Now, whenever yous run npm run build, you will see a cheat sheet with a sequence of commands to deploy to GitHub pages:

git commit -am                              "Salvage local changes"                            git checkout -B gh-pages git add -f build git commit -am                              "Rebuild website"                            git filter-branch -f --prune-empty --subdirectory-filter build git push -f origin gh-pages git checkout -

Y'all may re-create and paste them, or put them into a custom trounce script. You may also customize them for another hosting provider.

Note that GitHub Pages doesn't back up routers that use the HTML5 pushState history API under the hood (for example, React Router using browserHistory). This is because when in that location is a fresh folio load for a url like http://user.github.io/todomvc/todos/42, where /todos/42 is a frontend route, the GitHub Pages server returns 404 because it knows zippo of /todos/42. If you desire to add a router to a projection hosted on GitHub Pages, here are a couple of solutions:

• Yous could switch from using HTML5 history API to routing with hashes. If you lot use React Router, you can switch to hashHistory for this outcome, merely the URL will exist longer and more than verbose (for example, http://user.github.io/todomvc/#/todos/42?_k=yknaj). Read more about different history implementations in React Router.
• Alternatively, you can use a trick to teach GitHub Pages to handle 404 by redirecting to your index.html page with a special redirect parameter. You would need to add a 404.html file with the redirection lawmaking to the build folder earlier deploying your project, and yous'll need to add lawmaking handling the redirect parameter to index.html. You can find a detailed caption of this technique in this guide.

Heroku

Use the Heroku Buildpack for Create React App.
You can find instructions in Deploying React with Null Configuration.

Modulus

Meet the Modulus blog post on how to deploy your react app to Modulus.

At present

See this example for a zero-configuration single-command deployment with now.

Surge

Install the Surge CLI if you lot oasis't already by running npm install -g surge. Run the surge control and log in you or create a new business relationship. You just need to specify the build folder and your custom domain, and you are done.

              email: email@domain.com            password:              ********              projection path: /path/to/project/build                size: 7 files, i.viii MB              domain: create-react-app.surge.sh              upload: [====================] 100%, eta: 0.0s    propagate on CDN: [====================] 100%                plan: Free               users: email@domain.com          IP Accost: X.X.Ten.X      Success!              Project is published and running at create-react-app.surge.sh

Annotation that in gild to back up routers that utilise html5 pushState API, you may desire to rename the alphabetize.html in your build binder to 200.html before deploying to Surge. This ensures that every URL falls back to that file.

Something Missing?

If yous have ideas for more "How To" recipes that should exist on this page, let us know or contribute some!

How To Add Hidden Template In Stepik,

Source: https://github.com/Tom910/react-stepik

Posted by: vaughnreyel1980.blogspot.com

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