[RUBY] Testing for Error Messages: Rails Tutorial Notes-Chapter 7

Rails Tutorial 6.0 Chapter 7 7.3.4 Test at the time of failure Record of stumbling in the last exercise

Exercise content

"Write a test for the error message implemented in Listing 7.20. I'll leave it to you to test it in detail. I've provided a template for Listing 7.25 for your reference."


Use assert_select It's a good idea to check the HTML structure for improper login-specific elements.

Contents of the partial created immediately before (This content is inserted in new.html.erb)


<% if @user.errors.any? %>
  <div id="error_explanation">
    <div class="alert alert-danger">
      The form contains <%= pluralize(@user.errors.count, "error") %>.
    <% @user.errors.full_messages.each do |msg| %>
      <li><%= msg %></li>
    <% end %>
<% end %>

If @ user.errors exists, A div tag containing a specific class ("alert" & "alert-danger"), id ("error_explanation") is expanded

As long as this is included in the final HTML passed to the browser, assert_select'Selector (class: div.class, id: div # id)' Confirm it with

The completed form is as follows


require 'test_helper'

class UsersSignupTest < ActionDispatch::IntegrationTest

  test "invalid signup information" do
    assert_no_difference 'User.count' do
      post users_path, params: { user: { name: "",
                                         email: "user@invalid",
                                         password: "foo",
                                         password_confirmation: "bar"} }
    assert_template 'users/new'
    assert_select 'div.alert'
    assert_select 'div.alert-danger'
    assert_select 'div#error_explanation'


The structure verified by assert_select, Visually shown in Google Chrome developer tools スクリーンショット 2020-06-04 17.50.58.png

that's all

What I don't understand (for self-learning)

Use "" and "" properly I feel like "" is preferred when explicitly indicating that it is a string, The selector is specified as'''

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