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Run E2E tests on EAS Build

Learn how to set up and run E2E tests on EAS Build with popular libraries such as Detox.


EAS Build support for E2E testing is in a very early state. The intention of this guide is to explain how you can run E2E tests on the service today, without all of the affordances that we plan to build in the future. This guide will evolve over time as support for testing workflows in EAS Build improves.

With EAS Build, you can build a workflow for running E2E tests for your application. In this guide, you will learn how to use one of the most popular libraries (Detox) to do that.

This guide explains how to run E2E tests with Detox in a bare workflow project. You can use @config-plugins/detox for a managed project, but you may need to adjust some of the instructions in this guide to do so.

Running iOS tests

1. Initialize a new bare workflow project

Let's start by initializing a new Expo project, installing and configuring @config-plugins/detox, and running npx expo prebuild to generate the native projects.

Start with the following commands:

Terminal
# Initialize a new project
npx create-expo-app eas-tests-example
# cd into the project directory
cd eas-tests-example
# Install @config-plugins/detox
npm install --save-dev @config-plugins/detox

Now, open app.json and add the @config-plugins/detox plugin to your plugins list (this must be done before prebuilding). This will automatically configure the Android native code to support Detox.

app.json
{
  "expo": {
    // ...
    "plugins": ["@config-plugins/detox"]
  }
}

Run prebuild to generate the native projects:

Terminal
npx expo prebuild

2. Make home screen interactive

The first step to writing E2E tests is to have something to test - we have an empty app, so let's make our app interactive. We can add a button and display some new text when it's pressed. Later, we're going to write a test that's going to tap the button and check whether the text has been displayed.

👀 See the source code
App.js
import { StatusBar } from 'expo-status-bar';
import { useState } from 'react';
import { Pressable, StyleSheet, Text, View } from 'react-native';

export default function App() {
  const [clicked, setClicked] = useState(false);

  return (
    <View style={styles.container}>
      {!clicked && (
        <Pressable testID="click-me-button" style={styles.button} onPress={() => setClicked(true)}>
          <Text style={styles.text}>Click me</Text>
        </Pressable>
      )}
      {clicked && <Text style={styles.hi}>Hi!</Text>}
      <StatusBar style="auto" />
    </View>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#fff',
    alignItems: 'center',
    justifyContent: 'center',
  },
  hi: {
    fontSize: 30,
    color: '#4630EB',
  },
  button: {
    alignItems: 'center',
    justifyContent: 'center',
    paddingVertical: 12,
    paddingHorizontal: 32,
    borderRadius: 4,
    elevation: 3,
    backgroundColor: '#4630EB',
  },
  text: {
    fontSize: 16,
    lineHeight: 21,
    fontWeight: 'bold',
    letterSpacing: 0.25,
    color: 'white',
  },
});

3. Set up Detox

Install dependencies

Let's add two development dependencies to the project - jest and detox. jest (or mocha) is required because detox does not have its own test-runner.

Terminal
# Install jest and detox
npm install --save-dev jest detox
# Create Detox configuration files
npx detox init -r jest

See the official Detox docs at https://wix.github.io/Detox/docs/introduction/getting-started/ and https://wix.github.io/Detox/docs/guide/jest to learn about any potential updates to this process.

Configure Detox

Detox requires you to specify both the build command and path to the binary produced by it. Technically, the build command is not necessary when running tests on EAS Build, but allows you to run tests locally (for example, using npx detox build --configuration ios.release).

Edit detox.config.js and replace the configuration with:

detox.config.js
/** @type {Detox.DetoxConfig} */
module.exports = {
  logger: {
    level: process.env.CI ? 'debug' : undefined,
  },
  testRunner: {
    $0: 'jest',
    args: {
      config: 'e2e/jest.config.js',
      _: ['e2e'],
    },
  },
  artifacts: {
    plugins: {
      log: process.env.CI ? 'failing' : undefined,
      screenshot: 'failing',
    },
  },
  apps: {
    'ios.release': {
      type: 'ios.app',
      build:
        'xcodebuild -workspace ios/eastestsexample.xcworkspace -scheme eastestsexample -configuration Release -sdk iphonesimulator -arch x86_64 -derivedDataPath ios/build',
      binaryPath: 'ios/build/Build/Products/Release-iphonesimulator/eastestsexample.app',
    },
    'android.release': {
      type: 'android.apk',
      build:
        'cd android && ./gradlew :app:assembleRelease :app:assembleAndroidTest -DtestBuildType=release && cd ..',
      binaryPath: 'android/app/build/outputs/apk/release/app-release.apk',
    },
  },
  devices: {
    simulator: {
      type: 'ios.simulator',
      device: {
        type: 'iPhone 14',
      },
    },
    emulator: {
      type: 'android.emulator',
      device: {
        avdName: 'pixel_4',
      },
    },
  },
  configurations: {
    'ios.release': {
      device: 'simulator',
      app: 'ios.release',
    },
    'android.release': {
      device: 'emulator',
      app: 'android.release',
    },
  },
};

4. Write E2E tests

Next, we'll add our first E2E tests. Delete the auto-generated e2e/firstTest.e2e.js and create our own e2e/homeScreen.e2e.js with the following contents:

e2e/homeScreen.e2e.js
describe('Home screen', () => {
  beforeAll(async () => {
    await device.launchApp();
  });

  beforeEach(async () => {
    await device.reloadReactNative();
  });

  it('"Click me" button should be visible', async () => {
    await expect(element(by.id('click-me-button'))).toBeVisible();
  });

  it('shows "Hi!" after tapping "Click me"', async () => {
    await element(by.id('click-me-button')).tap();
    await expect(element(by.text('Hi!'))).toBeVisible();
  });
});

There are two tests in the suite:

  • One that checks whether the "Click me" button is visible on the home screen.
  • Another that verifies that tapping the button triggers displaying "Hi!".

Both tests assume the button has the testID set to click-me-button. See the source code for details.

5. Configure EAS Build

Now that we have configured Detox and written our first E2E test, let's configure EAS Build and run the tests in the cloud.

Create eas.json

The following command creates eas.json in the project's root directory:

Terminal
eas build:configure

Configure EAS Build

There are a few more steps to configure EAS Build for running E2E tests as part of the build:

  • Android tests:
    • Tests are run in the Android Emulator. You will define a build profile that builds your app for the emulator (produces an apk file).
    • Install the emulator and all its system dependencies.
  • iOS test:
    • Tests are run in the iOS Simulator. You will define a build profile that builds your app for the simulator.
    • Install the applesimutils command line util.
  • Configure EAS Build to run Detox tests after successfully building the app.

Edit eas.json and add the test build profile:

eas.json
{
  "build": {
    "test": {
      "android": {
        "gradleCommand": ":app:assembleRelease :app:assembleAndroidTest -DtestBuildType=release",
        "withoutCredentials": true
      },
      "ios": {
        "simulator": true
      }
    }
  }
}

Create eas-hooks/eas-build-pre-install.sh that installs the necessary tools and dependencies for the given platform:

eas-hooks/eas-build-pre-install.sh
#!/usr/bin/env bash

set -eox pipefail

if [[ "$EAS_BUILD_RUNNER" == "eas-build" && "$EAS_BUILD_PROFILE" == "test"* ]]; then
  if [[ "$EAS_BUILD_PLATFORM" == "android" ]]; then
    sudo apt-get --quiet update --yes

    # Install emulator & video bridge dependencies
    # Source: https://github.com/react-native-community/docker-android/blob/master/Dockerfile
    sudo apt-get --quiet install --yes \
      libc6 \
      libdbus-1-3 \
      libfontconfig1 \
      libgcc1 \
      libpulse0 \
      libtinfo5 \
      libx11-6 \
      libxcb1 \
      libxdamage1 \
      libnss3 \
      libxcomposite1 \
      libxcursor1 \
      libxi6 \
      libxext6 \
      libxfixes3 \
      zlib1g \
      libgl1 \
      pulseaudio \
      socat

    # Emulator must be API 31 -- API 32 and 33 fail due to https://github.com/wix/Detox/issues/3762
    sdkmanager --install "system-images;android-31;google_apis;x86_64"
    avdmanager --verbose create avd --force --name "pixel_4" --device "pixel_4" --package "system-images;android-31;google_apis;x86_64"
  else
    brew tap wix/brew
    brew install applesimutils
  fi
fi

Next, create eas-hooks/eas-build-on-success.sh with the following contents. The script runs different commands for Android and iOS. For iOS, the only command is detox test. For Android, it's a bit more complicated. You'll have to start the emulator before running the tests as detox sometimes seems to be having problems with starting the emulator on its own and it can get stuck on running the first test from your test suite. After the detox test run, there is a command that kills the previously started emulator.

eas-hooks/eas-build-on-success.sh
#!/usr/bin/env bash

function cleanup()
{
  echo 'Cleaning up...'
  if [[ "$EAS_BUILD_PLATFORM" == "android" ]]; then
    # Kill emulator
    adb emu kill &
  fi
}

if [[ "$EAS_BUILD_PROFILE" != "test" ]]; then
  exit
fi

# Fail if anything errors
set -eox pipefail
# If this script exits, trap it first and clean up the emulator
trap cleanup EXIT

ANDROID_EMULATOR=pixel_4

if [[ "$EAS_BUILD_PLATFORM" == "android" ]]; then
  # Start emulator
  $ANDROID_SDK_ROOT/emulator/emulator @$ANDROID_EMULATOR -no-audio -no-boot-anim -no-window -use-system-libs 2>&1 >/dev/null &

  # Wait for emulator
  max_retry=10
  counter=0
  until adb shell getprop sys.boot_completed; do
    sleep 10
    [[ counter -eq $max_retry ]] && echo "Failed to start the emulator!" && exit 1
    counter=$((counter + 1))
  done

  # Execute Android tests
  if [[ "$EAS_BUILD_PROFILE" == "test" ]]; then
    detox test --configuration android.release
  fi
else
  # Execute iOS tests
  if [[  "$EAS_BUILD_PROFILE" == "test" ]]; then
    detox test --configuration ios.release
  fi
fi

Edit package.json to use EAS Build hooks to run the above scripts on EAS Build:

package.json
{
  "scripts": {
    "eas-build-pre-install": "./eas-hooks/eas-build-pre-install.sh",
    "eas-build-on-success": "./eas-hooks/eas-build-on-success.sh"
  }
}

Don't forget to add executable permissions to eas-build-pre-install.sh and eas-build-on-success.sh. Run chmod +x eas-hooks/*.sh.

6. Run tests on EAS Build

Running the tests on EAS Build is like running a regular build:

Terminal
eas build -p all -e test

If you have set up everything correctly you should see the successful test result in the build logs:

7. Upload screenshots of failed test cases

This step is optional but highly recommended.

When an E2E test case fails, it can be helpful to see the screenshot of the application state. EAS Build makes it easy to upload any arbitrary build artifacts using the buildArtifactPaths field in eas.json.

Take screenshots for failed tests

Detox supports taking in-test screenshots of the device. The detox.config.js sample above includes a line to configure Detox to take screenshots of failed tests.

Configure EAS Build for screenshots upload

Edit eas.json and add buildArtifactPaths to the test build profile:

eas.json
{
  "build": {
    "test": {
      "android": {
        "gradleCommand": ":app:assembleRelease :app:assembleAndroidTest -DtestBuildType=release",
        "withoutCredentials": true
      },
      "ios": {
        "simulator": true
      },
      "buildArtifactPaths": ["artifacts/**/*.png"]
    }
  }
}

In contrast to applicationArchivePath, the build artifacts defined at buildArtifactPaths will be uploaded even if the build fails. All .png files from the artifacts directory will be packed into a tarball and uploaded to AWS S3. You can download them later from the build details page.

If you run E2E tests locally, remember to add artifacts to .gitignore:

.gitignore
artifacts/

Break a test and run a build

To test the new configuration, let's break a test and see that EAS Build uploads the screenshots.

Edit e2e/homeScreen.e2e.js and make the following change:

Run an iOS build with the following command and wait for it to finish:

Terminal
eas build -p ios -e test

After going to the build details page you should see that the build failed. Use the "Download artifacts" button to download and examine the screenshot:

Repository

The full example from this guide is available at https://github.com/expo/eas-tests-example.

Alternative approaches

Using development builds to speed up test run time

The above guide explains how to run E2E tests against a release build of your project, which requires executing a full native build before each test run. Re-building the native app each time you run E2E tests may not be desirable if only the project JavaScript or assets have changed. However, this is necessary for release builds because the app JavaScript bundle is embedded into the binary.

Instead, we can use development builds to load from a local development server or from published updates to save time and CI resources. This can be done by having your E2E test runner invoke the app with a URL that points to a specific update bundle URL, as described in the development builds deep linking URLs guide.

Development builds typically display an onboarding welcome screen when an app is launched for the first time, which intends to provide context about the expo-dev-client UI for developers. However, it can interfere with your E2E tests (which expect to interact with your app and not an onboarding screen). To skip the onboarding screen in a test environment, the query parameter disableOnboarding=1 can be appended to the project URL (an EAS Update URL or a local development server URL).

An example of such a Detox test is shown below. Full example code is available on the eas-tests-example repository.

e2e/homeScreen.e2e.js
const { openApp } = require('./utils/openApp');

describe('Home screen', () => {
  beforeEach(async () => {
    await openApp();
  });

  it('"Click me" button should be visible', async () => {
    await expect(element(by.id('click-me-button'))).toBeVisible();
  });

  it('shows "Hi!" after tapping "Click me"', async () => {
    await element(by.id('click-me-button')).tap();
    await expect(element(by.text('Hi!'))).toBeVisible();
  });
});
e2e/utils/openApp.js (new file)
const appConfig = require('../../../app.json');
const { resolveConfig } = require('detox/internals');

const platform = device.getPlatform();

module.exports.openApp = async function openApp() {
  const config = await resolveConfig();
  if (config.configurationName.split('.')[1] === 'debug') {
    return await openAppForDebugBuild(platform);
  } else {
    return await device.launchApp({
      newInstance: true,
    });
  }
};

async function openAppForDebugBuild(platform) {
  const deepLinkUrl = process.env.EXPO_USE_UPDATES
    ? // Testing latest published EAS update for the test_debug channel
      getDeepLinkUrl(getLatestUpdateUrl())
    : // Local testing with packager
      getDeepLinkUrl(getDevLauncherPackagerUrl(platform));

  if (platform === 'ios') {
    await device.launchApp({
      newInstance: true,
    });
    sleep(3000);
    await device.openURL({
      url: deepLinkUrl,
    });
  } else {
    await device.launchApp({
      newInstance: true,
      url: deepLinkUrl,
    });
  }

  await sleep(3000);
}

const getDeepLinkUrl = url =>
  `eastestsexample://expo-development-client/?url=${encodeURIComponent(url)}`;

const getDevLauncherPackagerUrl = platform =>
  `http://localhost:8081/index.bundle?platform=${platform}&dev=true&minify=false&disableOnboarding=1`;

const getLatestUpdateUrl = () =>
  `https://u.expo.dev/${getAppId()}?channel-name=test_debug&disableOnboarding=1`;

const getAppId = () => appConfig?.expo?.extra?.eas?.projectId ?? '';

const sleep = t => new Promise(res => setTimeout(res, t));
detox.config.js
/** @type {Detox.DetoxConfig} */
module.exports = {
  logger: {
    level: process.env.CI ? 'debug' : undefined,
  },
  testRunner: {
    $0: 'jest',
    args: {
      config: 'e2e/jest.config.js',
      _: ['e2e'],
    },
  },
  artifacts: {
    plugins: {
      log: process.env.CI ? 'failing' : undefined,
      screenshot: 'failing',
    },
  },
  apps: {
    'ios.debug': {
      type: 'ios.app',
      build:
        'xcodebuild -workspace ios/eastestsexample.xcworkspace -scheme eastestsexample -configuration Debug -sdk iphonesimulator -arch x86_64 -derivedDataPath ios/build',
      binaryPath: 'ios/build/Build/Products/Debug-iphonesimulator/eastestsexample.app',
    },
    'ios.release': {
      type: 'ios.app',
      build:
        'xcodebuild -workspace ios/eastestsexample.xcworkspace -scheme eastestsexample -configuration Release -sdk iphonesimulator -arch x86_64 -derivedDataPath ios/build',
      binaryPath: 'ios/build/Build/Products/Release-iphonesimulator/eastestsexample.app',
    },
    'android.debug': {
      type: 'android.apk',
      build:
        'cd android && ./gradlew :app:assembleDebug :app:assembleAndroidTest -DtestBuildType=debug && cd ..',
      binaryPath: 'android/app/build/outputs/apk/debug/app-debug.apk',
    },
    'android.release': {
      type: 'android.apk',
      build:
        'cd android && ./gradlew :app:assembleRelease :app:assembleAndroidTest -DtestBuildType=release && cd ..',
      binaryPath: 'android/app/build/outputs/apk/release/app-release.apk',
    },
  },
  devices: {
    simulator: {
      type: 'ios.simulator',
      device: {
        type: 'iPhone 14',
      },
    },
    emulator: {
      type: 'android.emulator',
      device: {
        avdName: 'pixel_4',
      },
    },
  },
  configurations: {
    'ios.debug': {
      device: 'simulator',
      app: 'ios.debug',
    },
    'ios.release': {
      device: 'simulator',
      app: 'ios.release',
    },
    'android.debug': {
      device: 'emulator',
      app: 'android.debug',
    },
    'android.release': {
      device: 'emulator',
      app: 'android.release',
    },
  },
};
eas-hooks/eas-build-on-success.sh
#!/usr/bin/env bash

function cleanup()
{
  echo 'Cleaning up...'
  if [[ "$EAS_BUILD_PLATFORM" == "android" ]]; then
    # Kill emulator
    adb emu kill &
  fi
}

if [[ "$EAS_BUILD_PROFILE" != "test"* ]]; then
  exit
fi

# Fail if anything errors
set -eox pipefail
# If this script exits, trap it first and clean up the emulator
trap cleanup EXIT

ANDROID_EMULATOR=pixel_4

if [[ "$EAS_BUILD_PLATFORM" == "android" ]]; then
  # Start emulator
  $ANDROID_SDK_ROOT/emulator/emulator @$ANDROID_EMULATOR -no-audio -no-boot-anim -no-window -use-system-libs 2>&1 >/dev/null &

  # Wait for emulator
  max_retry=10
  counter=0
  until adb shell getprop sys.boot_completed; do
    sleep 10
    [[ counter -eq $max_retry ]] && echo "Failed to start the emulator!" && exit 1
    counter=$((counter + 1))
  done


  # Execute Android tests
  if [[ "$EAS_BUILD_PROFILE" == "test" ]]; then
    detox test --configuration android.release
  fi
  if [[ "$EAS_BUILD_PROFILE" == "test_debug" ]]; then
    detox test --configuration android.debug
  fi
else
  # Execute iOS tests
  if [[  "$EAS_BUILD_PROFILE" == "test" ]]; then
    detox test --configuration ios.release
  fi
  if [[ "$EAS_BUILD_PROFILE" == "test_debug" ]]; then
    detox test --configuration ios.debug
  fi
fi
eas.json
{
  "build": {
    "test": {
      "android": {
        "gradleCommand": ":app:assembleRelease :app:assembleAndroidTest -DtestBuildType=release",
        "withoutCredentials": true
      },
      "ios": {
        "simulator": true
      }
    },
    "test_debug": {
      "android": {
        "gradleCommand": ":app:assembleDebug :app:assembleAndroidTest -DtestBuildType=debug",
        "withoutCredentials": true
      },
      "ios": {
        "buildConfiguration": "Debug",
        "simulator": true
      },
      "env": {
        "EXPO_USE_UPDATES": "1"
      },
      "channel": "test_debug"
    }
  }
}