detox

Graybox E2E Tests and Automation Library for Mobile

• About
• Getting Started
• Usage
• Options
• See it in Action
• The Detox API
• Dealing with flakiness
• Contributing to detox
• Some implementation details
• License

About

High velocity native mobile development requires us to adopt continuous integration workflows, which means our reliance on manual QA has to drop significantly. The most difficult part of automated testing on mobile is the tip of the testing pyramid - E2E. The core problem with E2E tests is flakiness - tests are usually not deterministic. We believe the only way to tackle flakiness head on is by moving from blackbox testing to graybox testing and that's where detox comes into play.

Development still in progress!

Please note that this library is still pre version 1.0.0 and under active development. The NPM version is higher because the name "detox" was transferred to us from a previous inactive package. Package can still break without respecting semver, though we try not to.

Getting Started

This is a step-by-step guide to help you add detox to your project.

You can also go through this short guide

If you used previous detox version, follow the migration guide.

Step 1: Installing Dependencies

• Install the latest version of brew.

• If you haven't already, install Node.js

   brew update && brew install node 

• You will also need fbsimctl installed:

   brew tap facebook/fb
   export CODE_SIGNING_REQUIRED=NO && brew install fbsimctl --HEAD

• Detox CLI

  detox-cli package should be installed globally, enabling usage of detox command line tools outside of your npm scripts.

  npm install -g detox-cli

Step 2: Add Detox

• Install detox:

   npm install detox --save-dev

• Install mocha:

   npm install mocha --save-dev

• Add this detox property to your package.json file:
  

   "detox": {
     "configurations": {
         "ios.sim.debug": {
           "binaryPath": "ios/build/Build/Products/Debug-iphonesimulator/example.app",
           "build": "xcodebuild -project ios/example.xcodeproj -scheme example -configuration Debug -sdk iphonesimulator -derivedDataPath ios/build",
           "type": "ios.simulator",
           "name": "iPhone 7"
         }
       } 
     }

• In the detox property you just copied, switch example with your project name.
  In "binaryPath": example.app should be <your_project_name>.app.
  In "build": example.xcodeproj should be <your_project_name>.xcodeproj and -scheme example should be
  -scheme <your_project_name>.

To test a release version, make sure to replace 'Debug' with 'Release' in the binaryPath and build properties. For full configuration options see the options section below.

Step 3: Create your first test (using mocha test runner)

Automatically:

detox init

Manually:

• Create an e2e folder in your project root.
• Create mocha.opts file with this content.
• Create init.js file with this content.
• Create your first test! myFirstTest.spec.js with content similar to this.

Step 4: Build Your App and Run Detox Tests

By using the detox command line tool, you can build and test your project easily.

• Build your app:

   detox build

• Test your app:

   detox test

That's it! Your first failing detox test! Next, we'll go over usage and how to make this test pass.

Usage

describe('Example', () => {
  beforeEach(async () => {
    await device.reloadReactNative();
  });
  
  it('should have welcome screen', async () => {
    await expect(element(by.id('welcome'))).toBeVisible();
  });
  
  it('should show hello screen after tap', async () => {
    await element(by.id('hello_button')).tap();
    await expect(element(by.label('Hello!!!'))).toBeVisible();
  });
  
  it('should show world screen after tap', async () => {
    await element(by.id('world_button')).tap();
    await expect(element(by.label('World!!!'))).toBeVisible();
  });
})

Detox uses Matchers to find elements in your app, Actions to emulate user interaction with those elements and Assertions to test how your app reacts.

Matchers

Matchers find elements in your app that match some property.

Whenever possible we recommend to match elements by id:

await element(by.id('random_id123'))

For other cases there is a variety of options:

// find an element by id (add a 'testID' prop to your view for this to work)
await element(by.id('tap_me'))

// find an element by text
await element(by.label('Tap Me'))

// find an element by id and by parent id
await element(by.id('Grandson883').withAncestor(by.id('Son883')))

// find an element by id and by child id
await element(by.id('Son883').withDescendant(by.id('Grandson883')))

// find an element by native view type
await element(by.type('RCTImageView'))

// multiple matchers
await element(by.id('UniqueId345').and(by.label('ID')))

// Choose from multiple elements matching the same matcher using index
await element(by.label('Product')).atIndex(2)

// find an element with an accessibility trait
await element(by.traits(['button'])

Example

To find the view with the id Son883

<View testID='Grandfather883' style={{padding: 8, backgroundColor: 'red', marginBottom: 10}}>
  <View testID='Father883' style={{padding: 8, backgroundColor: 'green'}}>
    <View testID='Son883' style={{padding: 8, backgroundColor: 'blue'}}>
      <View testID='Grandson883' style={{padding: 8, backgroundColor: 'purple'}} />
    </View>
  </View>
</View>

Use:

// any of the following will work
await element(by.id('Son883'))
await element(by.id('Son883').withAncestor(by.id('Father883')))
await element(by.id('Son883').withDescendant(by.id('Grandson883')))

Tip: To find the back button use:

 await element(by.traits(['button']).and(by.label('Back')))

A more detailed explanation on matchers can be found here

Actions

Actions are functions that emulate user behavior:

await element(by.label('Tap Me')).tap();
await element(by.label('Tap Me')).longPress();
await element(by.id('UniqueId819')).multiTap(3);
await element(by.id('UniqueId937')).typeText('passcode');
await element(by.id('UniqueId937')).replaceText('passcode again');
await element(by.id('UniqueId005')).clearText();
await element(by.id('ScrollView161')).scroll(100, 'down');
await element(by.id('ScrollView161')).scroll(100, 'up');
await element(by.id('ScrollView161')).scrollTo('bottom');
await element(by.id('ScrollView161')).scrollTo('top');

// directions: 'up'/'down'/'left'/'right', speed: 'fast'/'slow'
await element(by.id('ScrollView799')).swipe('down', 'fast');

Aseertions

Assertions test how your app behaves:

await expect(element(by.id('UniqueId204'))).toBeVisible();
await expect(element(by.id('UniqueId205'))).toBeNotVisible();
await expect(element(by.id('UniqueId205'))).toExist();
await expect(element(by.id('RandomJunk959'))).toNotExist();
await expect(element(by.id('UniqueId204'))).toHaveText('I contain some text');
await expect(element(by.id('UniqueId204'))).toHaveLabel('I contain some text');
await expect(element(by.label('I contain some text'))).toHaveId('UniqueId204');
await expect(element(by.id('UniqueId146'))).toHaveValue('0');

waitFor

Test async code with waitFor:

await waitFor(element(by.id('UniqueId336'))).toExist().withTimeout(2000);
await waitFor(element(by.label('Text5'))).toBeVisible().whileElement(by.id('ScrollView630')).scroll(50, 'down');

Device control

If this is a react native app, reload react native JS bundle

await device.reloadReactNative();

Install the app file defined in the current configuration

await device.installApp();

Uninstall the app defined in the current configuration

await device.uninstallApp();

Configuration Options

Set Xcode build path

By default, Xcode uses a randomized hidden path for outputting project build artifacts, called DerivedData. For ease of use (and better support in CI environments), it is recommended to change the project build path to a more convenient path.

• With your project opened in Xcode, select menu File ► Project Settings.... Click on Advanced..., select Custom and from the drop-down menu, select Relative to Derived Data.
• Build artifacts will now be created in a DerivedData folder next to your xcodeproj project.

Device Configuration

configurations holds all the device configurations, if there is only one configuration in configurations detox build and detox test will default to it, to choose a specific configuration use --configuration param

Configuration Params	Details
binaryPath	relative path to the ipa/app due to be tested (make sure you build the app in a project relative path)
type	device type, currently only ios.simulator is supported
name	device name, aligns to the device list avaliable through fbsimctl list for example, this is one line of the output of fbsimctl list: `A3C93900-6D17-4830-8FBE-E102E4BBCBB9
build	[optional] build command (either xcodebuild, react-native run-ios, etc...), will be later available through detox CLI tool.

Server Configuration

Detox can either initialize a server using a generated configuration, or can be overriden with a manual configuration:

	"detox": {
	  ...
	  "session": {
		"server": "ws://localhost:8099",
		"sessionId": "YourProjectSessionId"
	  }
	}

Test Root Folder

Optional: setting a custom test root folder

Applies when using detox-cli by running detox test command, default is e2e.

	"detox": {
	  ...
	  "specs": "path/to/tests"
	}

Build Configuration

In your detox config (in package.json) paste your build command into the configuration's build field. The build command will be triggered when running

You can choose to build your project in any of these ways...

• If there's only one configuration, you can simply use:

   detox build

• To choose a specific configuration:

   detox build --configuration yourConfiguration

• Building with xcodebuild:

   xcodebuild -project ios/YourProject.xcodeproj -scheme YourProject -sdk iphonesimulator -derivedDataPath ios/build

• Building using React Native, this is the least suggested way of running your build, since it also starts a random simulator and installs the app on it.

  react-native run-ios

Note: remember to update the app path in your package.json.

Test Configuration

• If there's only one configuration, you can simply use:

   detox test

• For multiple configurations, choose your configuration by passing --configuration param:

   detox test --configuration yourConfiguration

Faster test runs with app reuse

By default the app is removed, reinstalled and launched before each run. Starting fresh is critical in CI but in dev you might be able to save time between test runs and reuse the app that was previously installed in the simulator. To do so use the reuse flag and run your tests like this:detox test --reuse. This is especially useful with React Native DEV mode when making Javascript code changes that are getting picked up by the packager (and thus no reinstall is needed). This can save up to 7 seconds per run! You should not use this option if you made native code changes or if your app relies on local ("disk") storage.

See it in Action

Open the React Native demo project and follow the instructions

Not using React Native? you now have a pure native demo project too

The Detox API

Check the API Reference or see detox's own E2E test suite to learn the test API by example.

Dealing With Flakiness

See the Flakiness handbook

Contributing to Detox

If you're interested in working on detox core and contributing to detox itself, take a look here.

Some Implementation Details

• We let you write your e2e tests in JS (they can even be cross-platform)
• We use websockets to communicate (so it should be super fast and bi-directional)
• Both the app and the tester are clients, so we need the server to proxy between them
• We are relying on EarlGrey as our gray-box native library for iOS (espresso for Android later on)
• The JS tester controls EarlGrey by remote using a strange JSON protocol
• Instead of wrapping the zillion API calls EarlGrey supports, we implemented a reflection mechanism
• So the JS tester in low level actually invokes the native methods.. freaky
• We've abstracted this away in favor of a protractor-like api, see demo-react-native/e2e/example.spec.js
• See everything EarlGrey supports here and in this cheatsheet
• We use fbsimctl to control the simulator from the test, restart the app, etc

License

• detox by itself and all original source code in this repo is MIT
• detox relies on some important dependencies, their respective licenses are:
  • EarlGrey
  • FBSimulatorControl