shadows/framework/src/main/java/org/robolectric/shadows/ShadowTelephonyManager.java
@Implementation(minSdk = N)
  protected boolean isVoicemailVibrationEnabled(PhoneAccountHandle handle) {
    Boolean result = voicemailVibrationEnabledMap.get(handle);
    return result != null ? result : false;
  }
@Implementation(minSdk = N)
  protected boolean isVoicemailVibrationEnabled(PhoneAccountHandle handle) {
    Boolean result = voicemailVibrationEnabledMap.get(handle);
    return result != null ? result : false;
  }
Returns {@code null} by default or the value specified via {@link
#setVoicemailVibrationEnabled(PhoneAccountHandle, boolean)}.