Use the Espresso Device API to test your app when the device undergoes common
configuration changes, such as rotation and screen unfolding. The Espresso
Device API lets you simulate these configuration changes on a virtual device and
executes your tests synchronously, so only one UI action or assertion happens at
a time and your test results are more reliable. If you're new to writing UI
tests with Espresso, see its [documentation](https://developer.android.com/training/testing/espresso).

To use the Espresso Device API, you need the following:

- Android Studio Iguana or higher
- Android Gradle plugin 8.3 or higher
- Android Emulator 33.1.10 or higher
- Android virtual device that runs API level 24 or higher

## Set up your project for the Espresso Device API

To set up your project so it supports the Espresso Device API, do the following:

1. To let the test pass commands to the test device, add the
   `INTERNET` and `ACCESS_NETWORK_STATE` permissions to the manifest file in the `androidTest` source set:

   ```
     <uses-permission android:name="android.permission.INTERNET" />
     <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
     
   ```
2. Enable the `enableEmulatorControl` experimental flag in the
   `gradle.properties` file:

   ```
     android.experimental.androidTest.enableEmulatorControl=true
     
   ```
3. Enable the `emulatorControl` option in the module-level build
   script:

   ### Kotlin

   ```kotlin
     testOptions {
       emulatorControl {
         enable = true
       }
     }
     
   ```

   ### Groovy

   ```groovy
     testOptions {
       emulatorControl {
         enable = true
       }
     }
     
   ```
4. In the module-level build script, import the Espresso Device library
   into your project:

   ### Kotlin

   ```kotlin
     dependencies {
       androidTestImplementation("androidx.test.espresso:espresso-device:1.0.1")
     }
     
   ```

   ### Groovy

   ```groovy
     dependencies {
       androidTestImplementation 'androidx.test.espresso:espresso-device:1.0.1'
     }
     
   ```

## Test against common configuration changes

The Espresso Device API has multiple screen orientation and foldable states that
you can use to simulate device configuration changes.

### Test against screen rotation

Here's an example of how to test what happens to your app when the device screen
rotates:

1. First, for a consistent starting state set the device to portrait
   mode:

   ```kotlin
     import androidx.test.espresso.device.action.ScreenOrientation
     import androidx.test.espresso.device.rules.ScreenOrientationRule
     ...
     @get:Rule
     val screenOrientationRule: ScreenOrientationRule = ScreenOrientationRule(ScreenOrientation.PORTRAIT)
     
   ```
2. Create a test that sets the device to landscape orientation during test
   execution:

   ```kotlin
     @Test
     fun myRotationTest() {
       ...
       // Sets the device to landscape orientation during test execution.
       onDevice().setScreenOrientation(ScreenOrientation.LANDSCAPE)
       ...
     }
     
   ```
3. After the screen rotates, check that the UI adapts to the new layout as expected.

   ```kotlin
     @Test
     fun myRotationTest() {
       ...
       // Sets the device to landscape orientation during test execution.
       onDevice().setScreenOrientation(ScreenOrientation.LANDSCAPE)
       composeTestRule.onNodeWithTag("NavRail").assertIsDisplayed()
       composeTestRule.onNodeWithTag("BottomBar").assertDoesNotExist()
     }
     
   ```

### Test against screen unfolding

Here's an example of how to test what happens to your app if it's on a foldable
device and the screen unfolds:

1. First, test with the device in the folded state by calling
   `onDevice().setClosedMode()`. Make sure that your app's layout
   adapts to the compact screen width.

   ```kotlin
     @Test
     fun myUnfoldedTest() {
       onDevice().setClosedMode()
       composeTestRule.onNodeWithTag("BottomBar").assetIsDisplayed()
       composeTestRule.onNodeWithTag("NavRail").assetDoesNotExist()
       ...
     }
     
   ```
2. To transition to a fully unfolded state, call
   `onDevice().setFlatMode()`. Check that the app's layout adapts to
   the expanded size class.

   ```kotlin
     @Test
     fun myUnfoldedTest() {
       onDevice().setClosedMode()
       ...
       onDevice().setFlatMode()
       composeTestRule.onNodeWithTag("NavRail").assertIsDisplayed()
       composeTestRule.onNodeWithTag("BottomBar").assetDoesNotExist()
     }
     
   ```

## Specify what devices your tests need

If you're running a test that performs folding actions on a device that isn't
foldable, the test will likely fail. To execute only the tests that are relevant
to the running device, use the `@RequiresDeviceMode` annotation. The test runner
automatically skips running tests on devices that don't support the
configuration being tested. You can add the device requirement rule to each test
or an entire test class.

For example, to specify that a test should only be run on devices that support
unfolding to a flat configuration, add the following `@RequiresDeviceMode` code
to your test:  

    @Test
    @RequiresDeviceMode(mode = FLAT)
    fun myUnfoldedTest() {
      ...
    }