Trying to write my first Rails View Test in RSpec and failing with instance variable

Question

I have a (still) simple Rails application for books, and I want to test that the "show" page for an individual book contains that book's title.

The show.html.erb template is quite simple still, and as part of it, <%= @book.title %> is printed. However, RSpec is struggling before that. Here's the full code of show.html.erb_spec.rb:

require 'rails_helper'

RSpec.describe "books/show.html.erb", type: :view do
  context 'Show page' do
    let(:book) { create(:hobbit) }
  end
  it 'displays the book title on the show page' do
    assign(:book, book)
    render
    expect(rendered).to have_content(book.title)
  end
end

The factory for "hobbit" looks like this:

FactoryBot.define do
  factory :hobbit, class: Book do
    title { 'The Hobbit' }
    year { 1937 }
    rating { 5 }
    condition { 4 }
  end
  ...
end

And the error I get is relating to the "assign" statement in the spec. I don't get what the problem is - the show page should know an instance variable @book?

books/show.html.erb
  displays the book title on the show page (FAILED - 1)

Failures:

  1) books/show.html.erb displays the book title on the show page
     Failure/Error: assign(:book, book)
     
     NameError:
       undefined local variable or method `book' for #<RSpec::ExampleGroups::BooksShowHtmlErb "displays the book title on the show page" (./spec/views/books/show.html.erb_spec.rb:7)>
     # ./spec/views/books/show.html.erb_spec.rb:8:in `block (2 levels) in <top (required)>'

I am sure this is a very stupid beginner error but I couldn't find anything that helps me with this?

Answer 1

The simple problem was that I didn't install capybara!