@Test
public void testIsPremium() throws Exception {

    assertThat(user.isPremium()).isEqualTo(true);
    XingUser basicUser = new XingUser(null).premiumServices(Collections.<PremiumService>emptyList());
    assertThat(basicUser.isPremium()).isEqualTo(false);
    XingUser nullUser = new XingUser(null).premiumServices(null);
    assertThat(nullUser.isPremium()).isEqualTo(false);
}