Incremental spec suite hygiene

[eitoball]

Summary

Incremental cleanup of the RSpec suite: reduce class pollution, extract shared helpers, and chip away at .rubocop_todo.yml exclusions — without rewriting the intentional inline-DSL spec style.

Problem

The spec suite documents DSL behavior well, but accumulates maintenance cost:

Issue	Examples	Impact
Constants defined inside describe blocks	spec/comma/comma_spec.rb, AR/Mongoid specs	RuboCop Lint/ConstantDefinitionInBlock excluded
Repeated class Foo names across examples	Multiple files	Order-dependent pollution if examples leak
Long inline expected CSV strings	comma_spec.rb, users_controller_spec.rb	Hard to read diffs
Stale RuboCop todo entries	.rubocop_todo.yml	Masks fixable offenses in touched files

The project intentionally uses inline classes to show DSL usage — this issue is about hygiene, not replacing that pattern entirely.

Proposed approach (incremental)

1. Shared helper for anonymous comma classes

# spec/support/comma_class_helper.rb
def define_comma_class(&block)
  Class.new do
    class_eval(&block)
  end
end

Use in new/changed specs; migrate old ones opportunistically.

2. CSV expectation helper

def expect_csv(output, headers:, rows:)
  expected = CSV.generate { |csv| csv << headers; rows.each { |r| csv << r } }
  expect(output).to eq(expected)
end

Reduces copy-paste in comma_spec and controller specs.

3. Shared fixture models (optional)

Move stable models like Book / Isbn patterns to spec/support/models/ only where duplication exceeds benefit — keep Book in spec/non_rails_app/ruby_classes.rb as the canonical example.

4. RuboCop todo reduction

When touching a spec file, fix or narrow exclusions instead of adding new ones.

Files likely involved

• spec/support/ (new helpers)
• spec/comma/comma_spec.rb
• spec/comma/data_extractor_spec.rb
• spec/comma/header_extractor_spec.rb
• spec/controllers/users_controller_spec.rb
• .rubocop_todo.yml

Acceptance criteria

• At least one support helper added and used in 2+ spec files
• No spec behavior changes (same examples, same expectations)
• Document helper usage in a short comment at top of spec/support/comma_class_helper.rb
• Reduce at least one entry from .rubocop_todo.yml OR file an explicit follow-up list of remaining exclusions
• Not required: migrate every inline class in one PR

Labels (suggested)

refactor, tests, good first issue

Depends on

None. Best done alongside other refactor PRs (touch spec once).

Out of scope

• Full spec rewrite
• Changing Appraisal matrix or CI structure