String getUserLogin() {
    return configuration.get(USER_LOGIN_ATTRIBUTE).orElseThrow(() -> new IllegalArgumentException("User login attribute is missing"));
  }
@Test
  public void fail_to_get_user_login_attribute_when_null() {
    assertThatThrownBy(() -> underTest.getUserLogin())
      .isInstanceOf(IllegalArgumentException.class)
      .hasMessage("User login attribute is missing");
  }