@Test
public void testEnterOnError() {

    // リフレクション経由で、Action内部のフィールドを初期化
    Auth auth = new Auth();
    Account acc = new Account();
    acc.setName("error");
    acc.setEmail("test@test");
    auth.setAccount(acc);
    PrivateUtil.setField(target, "auth", auth);
    String act = target.enter();
    
    assertThat(act, nullValue());
    assertThat(auth.isLoggedIn(), is(false));
}