rubocop-aaa

rubocop-aaa

RuboCop cop that enforces the Arrange-Act-Assert pattern in Ruby test code.

Install

# Gemfile
group :development, :test do
  gem 'rubocop-aaa', require: false
end

Usage

Enable the cop in your .rubocop.yml:

require:
  - rubocop-aaa

AAA/Pattern:
  Enabled: true
  Include:
    - 'spec/**/*.rb'
    - 'test/**/*.rb'

What it checks

Every test block (it, test, specify, example by default) must contain three marker comments in order:

it 'adds' do
  # arrange
  a = 1
  b = 2

  # act
  sum = a + b

  # assert
  expect(sum).to eq(3)
end

Configuration

AAA/Pattern:
  TestFunctions:
    - it
    - test
    - specify
    - example
  Labels:
    arrange: [arrange]
    act:     [act]
    assert:  [assert]
  CaseSensitive: false
  AllowEmptySection: true

Given / When / Then

AAA/Pattern:
  Labels:
    arrange: [given]
    act:     [when]
    assert:  [then]

Japanese

Japanese phrasing varies, so no preset ships — configure with the wording your team uses:

AAA/Pattern:
  Labels:
    arrange: [準備, 前準備]
    act:     [実行]
    assert:  [検証, 確認]

Auto-correct

When all three section comments are missing, rubocop -a (or rubocop --autocorrect) inserts a # arrange / # act / # assert template at the top of the block. You then move each comment above the code that belongs to it.

Other cases — one or two sections missing, wrong order, empty section — are reported with explicit hints in the offense message but are not auto-corrected, because the correct insertion point depends on the test's intent.

License

MIT