Device Configuration

Robolectric makes it easy to simulate a variety of device configurations. In particular, the properties that make up the android.content.res.Configuration class can be specified at the test method, test class, package, or suite level, as described here.

Specifying Device Configuration

The Android device configuration can be specified using the qualifiers config property:

@Test @Config(qualifiers = "fr-rFR-w360dp-h640dp-xhdpi")
public void testItOnFrenchNexus5() { ... }

From version 3.6 on, Robolectric parses the qualifiers property according to the rules set forth here (but with no preceding directory name), and sets up the Android simulation environment with a corresponding configuration. The system’s Configuration, Display and DisplayMetrics objects will all reflect the specified configuration, the locale will be set, and appropriate resources will be selected.

For unspecified properties, Robolectric picks consistent values based on the properties that have been specified, or uses default values as follows:

Cumulative Qualifiers

By default, specifying qualifiers causes any previous specification of qualifiers to be ignored. For example, qualifiers at the test method level occlude qualifiers at the test class level. However, if the qualifiers config property starts with a ‘+’ (plus sign), it is interpreted as an overlay to any higher-level qualifiers that have been specified:

@Config(qualifiers = "xlarge-port")
class MyTest {
  public void testItWithXlargePort() { ... } // config is "xlarge-port"

  @Config(qualifiers = "+land")
  public void testItWithXlargeLand() { ... } // config is "xlarge-land"

  @Config(qualifiers = "land")
  public void testItWithLand() { ... } // config is "normal-land"
}

Values for unspecified properties are calculated, and rules are applied, after all configs have been merged.

Changing Device Configuration

The device configuration can be changed within a test using RuntimeEnvironment.setQualifiers():

@Test @Config(qualifiers = "+port")
public void testOrientationChange() {
  controller = Robolectric.buildActivity(MyActivity.class);
  controller.setup();
  // assert that activity is in portrait mode
  RuntimeEnvironment.setQualifiers("+land");
  controller.configurationChange();
  // assert that activity is in landscape mode
}

The string parameter to setQualifiers() has the same rules as Config.qualifiers.

Note that RuntimeEnvironment.setQualifiers() updates the system and application resources with the new configuration, but does not trigger any action on extant activities or other components. ActivityController.configurationChange() can be used to simulate the sequence of events that take place on a device when its configuration changes.

If the activity is configured to handle the configuration changes, ActivityController.configurationChange() will call the activity’s onConfigurationChanged() method. If not, ActivityController destroys and recreates the activity.

Simulating Displays

Robolectric allows display properties to be changed during a test using setters on ShadowDisplay. For Jelly Bean MR1 and up, multiple displays can be simulated using APIs on ShadowDisplayManager. See their documentation for more details.