Class: RuboCop::Cop::Vicenzo::RSpec::CompetingSubjects

Inherits:
RSpec::Base
  • Object
show all
Includes:
DescribedMethod, ExpectationTarget, PremiseTracking
Defined in:
lib/rubocop/cop/vicenzo/rspec/competing_subjects.rb

Overview

Two or more definitions the expectations assert on, in a group that declares no subject, are contexts that were never written.

A group speaks about one subject. When its examples each assert on a different definition, the group is not one scenario with several facts: it is several scenarios sharing a roof, and the circumstance that tells them apart - the one a context would have named - lives only in the definitions' names and in the reader's head.

The fix is structural, and it is never to pick one of them to promote. Which shape it takes depends on what the definitions are to this group, and working that out is the whole job - which is why the offense names what was found rather than prescribing a repair:

  1. They are different scenarios. Give each its own context, saying out loud the circumstance it stands for, and let each declare the subject it is about. What was encoded in record_1 / record_2 becomes a sentence, and the example shrinks to the outcome alone.
  2. One outcome covers them all. Then they were never subjects: they are the premise. Move them into a before, unnamed, and assert on the collection they belong to.

Both are corrections to the spec. Neither is silencing the cop: a definition named record_1 is the shape this smell takes, so renaming it settles nothing, and an inline disable directive keeps the hidden scenario hidden - which is the cost being paid here.

A group that already declares a subject is left alone - there the subject is settled and the other definitions are premises, whatever their names suggest.

Examples:

# bad - two subjects under one roof; the circumstances are only in the names
describe '#approved?' do
  let!(:reviewed_post) { create(:post, reviewed_at: Time.current) }
  let!(:draft_post) { create(:post) }

  it { expect(reviewed_post).to be_approved }
  it { expect(draft_post).not_to be_approved }
end

# good - one context per scenario, each with its own subject
describe '#approved?' do
  context 'when the post has been reviewed' do
    subject(:post) { create(:post, reviewed_at: Time.current) }

    it { is_expected.to be_approved }
  end

  context 'without a review' do
    subject(:post) { create(:post) }

    it { is_expected.not_to be_approved }
  end
end

when one outcome covers every record, they are the premise

# bad - two records named as if each were a subject
describe '#deactivate' do
  let!(:pending_alert) { create(:alert, :pending) }
  let!(:firing_alert) { create(:alert, :firing) }

  it 'dismisses every alert', :aggregate_failures do
    monitor.deactivate

    expect(pending_alert.reload).to be_dismissed
    expect(firing_alert.reload).to be_dismissed
  end
end

# good - the records are the premise, and the outcome is about the collection
describe '#deactivate' do
  before do
    create(:alert, :pending)
    create(:alert, :firing)
  end

  it 'dismisses every alert' do
    monitor.deactivate

    expect(monitor.alerts).to contain_exactly(be_dismissed, be_dismissed)
  end
end

records a single expectation compares are not competing subjects

# good - both records build the one answer the example is about
describe '.recent' do
  let!(:recent_order) { create(:order, created_at: 1.day.ago) }
  let!(:old_order) { create(:order, created_at: 1.year.ago) }

  it { expect(described_class.recent).to contain_exactly(recent_order) }
end

Constant Summary collapse

MSG = 
'The expectations here are about %<names>s, so this group has no one subject. Work out ' \
'what these definitions are to it, and let the structure say so.'

Constants included from PremiseTracking

PremiseTracking::SETUP_HOOKS

Constants included from ExpectationTarget

ExpectationTarget::EXPECTATION_RUNNERS, ExpectationTarget::MESSAGE_MATCHERS

Constants included from DescribedMethod

DescribedMethod::BARE_METHOD_DESCRIPTION, DescribedMethod::PREFIXED_METHOD_DESCRIPTION

Instance Method Summary collapse

Methods included from PremiseTracking

#premise_name, #root_receiver_name

Instance Method Details

#on_block(node) ⇒ Object Also known as: on_numblock, on_itblock 



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# File 'lib/rubocop/cop/vicenzo/rspec/competing_subjects.rb', line 105

def on_block(node)
  return unless example_group?(node)

  names = competing_names(node)

  return if names.size < 2

  add_offense(node.send_node, message: format(MSG, names: names.join(', ')))
end