很奇怪的问题，测试页面是否有 head，竟然测不通！

expect(page).to have_selector(:xpath, "/html/head")

报错：

Failure/Error: expect(page).to have_selector(:xpath, "/html/head") expected to find visible xpath "/html/head" but there were no matches. Also found "", which matched the selector but not all filters.

难道我的页面没有 head? 可是我检查过，响应很正常，head 和 body 都是有的。

body 和 title 是可以测通的。

expect(page).to have_selector(:xpath, "/html/body")

expect(page).to have_title(@home.title + ' - ' + I18n.t('app_name'))