shadows/framework/src/main/java/org/robolectric/RuntimeEnvironment.java
public static void setQualifiers(String newQualifiers) {
    Configuration configuration;
    DisplayMetrics displayMetrics = new DisplayMetrics();
    if (newQualifiers.startsWith("+")) {
      configuration = new Configuration(Resources.getSystem().getConfiguration());
      displayMetrics.setTo(Resources.getSystem().getDisplayMetrics());
    } else {
      configuration = new Configuration();
    }
    Bootstrap.applyQualifiers(newQualifiers, getApiLevel(), configuration, displayMetrics);

    Resources systemResources = Resources.getSystem();
    systemResources.updateConfiguration(configuration, displayMetrics);

    if (application != null) {
      application.getResources().updateConfiguration(configuration, displayMetrics);
    }
  }
public static void setQualifiers(String newQualifiers) {
    Configuration configuration;
    DisplayMetrics displayMetrics = new DisplayMetrics();
    if (newQualifiers.startsWith("+")) {
      configuration = new Configuration(Resources.getSystem().getConfiguration());
      displayMetrics.setTo(Resources.getSystem().getDisplayMetrics());
    } else {
      configuration = new Configuration();
    }
    Bootstrap.applyQualifiers(newQualifiers, getApiLevel(), configuration, displayMetrics);

    Resources systemResources = Resources.getSystem();
    systemResources.updateConfiguration(configuration, displayMetrics);

    if (application != null) {
      application.getResources().updateConfiguration(configuration, displayMetrics);
    }
  }
Overrides the current device configuration.

If `newQualifiers` starts with a plus (`+`), the prior configuration is used as the base
configuration, with the given changes applied additively. Otherwise, default values are used
for unspecified properties, as described [here](http://robolectric.org/device-configuration/).

@param newQualifiers the qualifiers to apply