Unclear working of shared_examples inside a context in a shared_context

[lvonk]

Subject of the issue

Adding a context inside a shared_context breaks the working of include_examples.

Your environment

• Ruby version: 3.2
• rspec-core version: 3.12

Steps to reproduce

RSpec.shared_examples 'shared examples' do
  let(:foos) { [bar] }

  it 'uses the foo provided by the context' do
    expect(foos.length).to eq 2
  end
end

RSpec.shared_context 'shared context' do
  context 'my context' do
    include_examples 'shared examples'
  end
end

describe 'my test' do
  include_context 'shared context' do
    let(:foos) { [1, 2] }
  end
end

Expected behavior

The test to pass.

The test will pass if I change the shared_context (and optionally spec) to

RSpec.shared_context 'shared context' do
  include_examples 'shared examples'
end

describe 'my test' do
  context 'my context' do
    include_context 'shared context' do
      let(:foos) { [1, 2] }
    end
  end
end

Actual behavior

NameError: undefined local variable or method `bar' for #<RSpec::ExampleGroups::MyTest::MyContext "uses the foo provided by the context" (./spec/foo_spec.rb:2)>

  0) my test my context uses the foo provded by the context
     Failure/Error: let(:foos) { [bar] }

     NameError:
       undefined local variable or method `bar' for #<RSpec::ExampleGroups::MyTest::MyContext "uses the foo provided by the context"

Is this a bug or can't you use a context within a shared_context like this?

[pirj]

It may not be obvious at a glance, but the [bar] foos is defined closes to the example itself than the one in a block passed to include_context. And this works as intended.
I don’t feel that this is a good way of parameterizing an included example group, but can’t advise on a better approach in such a simplified/obfuscated context.

[lvonk]

Perhaps this examples helps clarify what I want to achieve:

LineItem = Data.define(:amount, :quantity)

module SharedExamples
  LINE_ITEMS = 'Line items'

  RSpec.shared_examples LINE_ITEMS do
    let(:expected_payroll_line_item) { LineItem.new(amount: 10, quantity: 1) }

    let(:expected_line_items) { [expected_line_item_for_subscription, expected_payroll_line_item] }

    it 'creates the correct line items for subscription and payroll' do
      expect(system_under_test).to eq(expected_line_items)
    end
  end
end

module SharedContext
  BILLING = 'Billing'

  RSpec.shared_context BILLING, shared_context: :metadata do |_args = {}|
    let(:current_date) { Date.new(2024, 5, 1) }

    include_examples SharedExamples::LINE_ITEMS

    context 'before may 2024' do
      let(:current_date) { Date.new(2024, 4, 1) }

      include_examples SharedExamples::LINE_ITEMS do
        let(:expected_payroll_line_item) { LineItem.new(amount: 10, quantity: 2) }
      end
    end
  end
end

describe 'billing spec' do
  let(:system_under_test) do
    next [] if plan == 'b'

    if current_date < Date.new(2024, 5, 1)
      [LineItem.new(amount: 5, quantity: 1), LineItem.new(amount: 10, quantity: 2)]
    else
      [LineItem.new(amount: 5, quantity: 1), LineItem.new(amount: 10, quantity: 1)]
    end
  end

  context 'plan A' do
    let(:plan) { 'a' }
    let(:expected_line_item_for_subscription) { LineItem.new(amount: 5, quantity: 1) }
    include_context SharedContext::BILLING
  end

  context 'plan B' do
    let(:plan) { 'b' }
    include_context SharedContext::BILLING do
      let(:expected_line_items) { [] }
    end
  end
end

So the test describes for which plan I expect which line_items. The shared context defines several contexts with tests within a certain plan. The shared examples contains the test and assertion to execute each time.

If you have any advice to improve this that would be really helpful.

[JonRowe]

The indirection is whats causing you issues there, both contexts and examples are creating contexts so the lets in the examples take precedence, you could do a method define check in the examples or you could restructure it:

# frozen_string_literal: true

require 'date'

LineItem = Data.define(:amount, :quantity)

module SharedExamples
  LINE_ITEMS = 'Line items'

  RSpec.shared_examples LINE_ITEMS do
    it 'creates the correct line items for subscription and payroll' do
      expect(system_under_test).to eq(expected_line_items)
    end
  end
end

module SharedContext
  BILLING = 'Billing'

  RSpec.shared_context BILLING, shared_context: :metadata do |_args = {}|
    let(:current_date) { Date.new(2024, 5, 1) }
    let(:expected_payroll_line_item) { LineItem.new(amount: 10, quantity: 1) }
    let(:expected_line_items) { [expected_line_item_for_subscription, expected_payroll_line_item] }

    include_examples SharedExamples::LINE_ITEMS

    context 'before may 2024' do
      let(:current_date) { Date.new(2024, 4, 1) }
      let(:expected_payroll_line_item) { LineItem.new(amount: 10, quantity: 2) }

      include_examples SharedExamples::LINE_ITEMS
    end
  end
end

RSpec.describe 'billing spec' do
  let(:system_under_test) do
    next [] if plan == 'b'

    if current_date < Date.new(2024, 5, 1)
      [LineItem.new(amount: 5, quantity: 1), LineItem.new(amount: 10, quantity: 2)]
    else
      [LineItem.new(amount: 5, quantity: 1), LineItem.new(amount: 10, quantity: 1)]
    end
  end

  context 'plan A' do
    let(:plan) { 'a' }
    let(:expected_line_item_for_subscription) { LineItem.new(amount: 5, quantity: 1) }
    include_context SharedContext::BILLING
  end

  context 'plan B' do
    let(:plan) { 'b' }
    include_context SharedContext::BILLING do
      let(:expected_line_items) { [] }
    end
  end
end

[lvonk]

Thanks for your advice, I really appreciate it. I went for the restructuring approach.