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How can you set up an rspec so that the render is called only once for all of its specs?

I have the following view specification:

describe "carts/show" do
  before(:each) do
    book = build_stubbed(:product, title: "book")
    car = build_stubbed(:product, title: "car")
    line_item1 = build_stubbed(:line_item, product: book, quantity: 3)
    line_item2 = build_stubbed(:line_item, product: car, quantity: 1)
    @cart = assign(:cart, build_stubbed(:cart, line_items: [line_item1, line_item2]))
    render
  end

  it "displays a single car" do
    assert_select "li", text: "1 time: car"
  end
  it "displays 3 books" do
    assert_select "li", text: "3 times: book"
  end
  it "has exactly 2 items" do
    assert_select "li", 2
  end

end

These specifications work as expected. However, because the setup is in a block before(:each)

, the setup method is render

called once per block. It's pretty slow. Ideally, they only need to be called once for the entire block describe

.

I thought changing before(:each)

to would before(:all)

fix this, but I got the error (line 16 in show.html.erb_spec.rb - call render

):

NoMethodError: undefined method `example_group' for nil:NilClass
~/.rvm/gems/ruby-1.9.3-p125/gems/rspec-rails-2.12.0/lib/rspec/rails/example/view_example_group.rb:106:in `_default_file_to_render'
~/.rvm/gems/ruby-1.9.3-p125/gems/rspec-rails-2.12.0/lib/rspec/rails/example/view_example_group.rb:112:in `_default_render_options'
~/.rvm/gems/ruby-1.9.3-p125/gems/rspec-rails-2.12.0/lib/rspec/rails/example/view_example_group.rb:45:in `render'
show.html.erb_spec.rb:16:in `block (2 levels) in <top (required)>'
~/.rvm/gems/ruby-1.9.3-p125/gems/rspec-core-2.12.1/lib/rspec/core/hooks.rb:23:in `instance_eval'
~/.rvm/gems/ruby-1.9.3-p125/gems/rspec-core-2.12.1/lib/rspec/core/hooks.rb:23:in `run'
~/.rvm/gems/ruby-1.9.3-p125/gems/rspec-core-2.12.1/lib/rspec/core/hooks.rb:106:in `run'
~/.rvm/gems/ruby-1.9.3-p125/gems/rspec-core-2.12.1/lib/rspec/core/hooks.rb:424:in `run_hook'
~/.rvm/gems/ruby-1.9.3-p125/gems/rspec-core-2.12.1/lib/rspec/core/example_group.rb:319:in `run_before_all_hooks'
~/.rvm/gems/ruby-1.9.3-p125/gems/rspec-core-2.12.1/lib/rspec/core/example_group.rb:368:in `run'
~/.rvm/gems/ruby-1.9.3-p125/gems/rspec-core-2.12.1/lib/rspec/core/command_line.rb:28:in `block (2 levels) in run'
~/.rvm/gems/ruby-1.9.3-p125/gems/rspec-core-2.12.1/lib/rspec/core/command_line.rb:28:in `map'
~/.rvm/gems/ruby-1.9.3-p125/gems/rspec-core-2.12.1/lib/rspec/core/command_line.rb:28:in `block in run'
~/.rvm/gems/ruby-1.9.3-p125/gems/rspec-core-2.12.1/lib/rspec/core/reporter.rb:34:in `report'
~/.rvm/gems/ruby-1.9.3-p125/gems/rspec-core-2.12.1/lib/rspec/core/command_line.rb:25:in `run'
~/.rvm/gems/ruby-1.9.3-p125/gems/rspec-core-2.12.1/lib/rspec/core/runner.rb:80:in `run'
~/.rvm/gems/ruby-1.9.3-p125/gems/rspec-core-2.12.1/lib/rspec/core/runner.rb:17:in `block in autorun'

I don't know what else I could do here. What is the correct way to solve this problem?

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2 answers


RSpec-Rails rendering definitely assumes that it occurs in every test, which will make it a little awkward and we need to play with the internal state from its appearance.

Due to the shaking around rspec-rails, it looks like it is delegating its call render

ActionView::TestCase::Behavior#render

. @rendered

seems to be a state that matters (and probably @view

does), but I have no idea if this will lead to more errors.



Here's my totally untested approach:

describe "carts/show" do

  # Memoize the view across test runs for speed; this is some dangerous
  # spelunking in internal state, though!
  rendered_view    = nil
  rendered_content = nil

  before(:each) do
    if rendered_view && rendered_content
      @view     = rendered_view
      @rendered = rendered_content
    else
      book = build_stubbed(:product, title: "book")
      car = build_stubbed(:product, title: "car")
      line_item1 = build_stubbed(:line_item, product: book, quantity: 3)
      line_item2 = build_stubbed(:line_item, product: car, quantity: 1)
      @cart = assign(:cart, build_stubbed(:cart, line_items: [line_item1, line_item2]))

      render

      rendered_view    = @view
      rendered_content = @rendered
    end
  end

  it "displays a single car" do
    assert_select "li", text: "1 time: car"
  end
  it "displays 3 books" do
    assert_select "li", text: "3 times: book"
  end
  it "has exactly 2 items" do
    assert_select "li", 2
  end

end
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It's not perfect, but you can use shared_subject

To use it, you essentially:

  • Replace "subject" with "shared_subject" to share the first acrooss result of the entire context.
  • (optional) replace 'before (: each)' blocks with 'shared_setup'
  • Done. The subject will be passed into one, single context (the nested ones will be re-configured again).


So your example would look like this:

describe "carts/show" do
  shared_subject do
    book = build_stubbed(:product, title: "book")
    car = build_stubbed(:product, title: "car")
    line_item1 = build_stubbed(:line_item, product: book, quantity: 3)
    line_item2 = build_stubbed(:line_item, product: car, quantity: 1)
    @cart = assign(:cart, build_stubbed(:cart, line_items: [line_item1, line_item2]))
    render
  end

  it "displays a single car" do
    assert_select "li", text: "1 time: car"
  end
  it "displays 3 books" do
    assert_select "li", text: "3 times: book"
  end
  it "has exactly 2 items" do
    assert_select "li", 2
  end

end
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