ruby-on-rails – Capybara不会填写我的登录字段

require 'spec_helper'

describe "the login process" do
  it "signs me in" do
    visit '/login'    
    fill_in 'user_username',:with => 'Admin'
    fill_in 'user_password',:with => 'Password'
  end
end

当我运行测试时,它失败并出现以下错误：

1) the login process signs me in
    Failure/Error: fill_in 'user_username',:with => 'Admin'
    Capybara::ElementNotFound:
    no text field,text area or password field with id,name,or label 'user_username' found
    # (eval):2:in `fill_in'
    # ./spec/integration/login_spec.rb:7:in `block (2 levels) in <top (required)>'

但是当我使用打印页面的内容时

print page.html

我可以清楚地看到元素ID是正确的

<h2>Already Have an Account?</h2>
<form accept-charset="UTF-8" action="/login" id="sidebar_login" method="post">
<div style="margin:0;padding:0;display:inline">
    <input name="utf8" type="hidden" value="?"><input name="authenticity_token" type="hidden" value="DccrBxhdS7WTAM/iEd08L4z9zt8MjBKTxQ0s6lMVIAA=">
</div>
<div class="form"></div>
<div class="login_form_widget">
Username
<div class="inputdiv_widget">
    <input class="textfield" id="user_username" name="user[username]" type="text">
</div>
Password
<div class="inputdiv_widget">
    <input class="textfield" id="user_password" name="user[password]" type="password">
</div>

我已经尝试使用元素的id(user_username)和name(用户[username]),所有这些都具有相同的结果.这里有什么我想念的吗？