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Testing Attachment Style Management in Paperclip

This test suite validates Paperclip’s attachment styles management functionality, focusing on handling missing styles and style registration. It ensures proper tracking and comparison of attachment styles across model definitions and file persistence.

Test Coverage Overview

The test suite comprehensively covers Paperclip’s attachment styles management system, including:

Style registration and persistence
Path configuration for styles storage
Style comparison and difference detection
Dynamic style updates across models
Lambda-style handling edge cases

Implementation Analysis

The testing approach utilizes RSpec’s behavior-driven development paradigm with focused unit tests. It employs before/after hooks for setup/teardown and leverages Paperclip’s internal APIs for style management. The implementation demonstrates proper isolation and state management between tests.

Technical Details

Testing Framework: RSpec
File Management: YAML storage for styles
Setup: Custom model rebuilding
Dependencies: ActiveRecord integration
Configuration: Dynamic style definition support

Best Practices Demonstrated

The test suite exemplifies several testing best practices including proper test isolation, comprehensive edge case coverage, and clear test organization. It demonstrates effective use of setup/teardown hooks, explicit state management, and thorough validation of both successful and edge case scenarios.

thoughtbot/paperclip

spec/paperclip/paperclip_missing_attachment_styles_spec.rb

            
require 'spec_helper'

describe 'Missing Attachment Styles' do
  before do
    Paperclip::AttachmentRegistry.clear
  end

  after do
    File.unlink(Paperclip.registered_attachments_styles_path) rescue nil
  end

  it "enables to get and set path to registered styles file" do
    assert_equal ROOT.join('tmp/public/system/paperclip_attachments.yml').to_s, Paperclip.registered_attachments_styles_path
    Paperclip.registered_attachments_styles_path = '/tmp/config/paperclip_attachments.yml'
    assert_equal '/tmp/config/paperclip_attachments.yml', Paperclip.registered_attachments_styles_path
    Paperclip.registered_attachments_styles_path = nil
    assert_equal ROOT.join('tmp/public/system/paperclip_attachments.yml').to_s, Paperclip.registered_attachments_styles_path
  end

  it "is able to get current attachment styles" do
    assert_equal Hash.new, Paperclip.send(:current_attachments_styles)
    rebuild_model styles: {croppable: '600x600>', big: '1000x1000>'}
    expected_hash = { Dummy: {avatar: [:big, :croppable]}}
    assert_equal expected_hash, Paperclip.send(:current_attachments_styles)
  end

  it "is able to save current attachment styles for further comparison" do
    rebuild_model styles: {croppable: '600x600>', big: '1000x1000>'}
    Paperclip.save_current_attachments_styles!
    expected_hash = { Dummy: {avatar: [:big, :croppable]}}
    assert_equal expected_hash, YAML.load_file(Paperclip.registered_attachments_styles_path)
  end

  it "is able to read registered attachment styles from file" do
    rebuild_model styles: {croppable: '600x600>', big: '1000x1000>'}
    Paperclip.save_current_attachments_styles!
    expected_hash = { Dummy: {avatar: [:big, :croppable]}}
    assert_equal expected_hash, Paperclip.send(:get_registered_attachments_styles)
  end

  it "is able to calculate differences between registered styles and current styles" do
    rebuild_model styles: {croppable: '600x600>', big: '1000x1000>'}
    Paperclip.save_current_attachments_styles!
    rebuild_model styles: {thumb: 'x100', export: 'x400>', croppable: '600x600>', big: '1000x1000>'}
    expected_hash = { Dummy: {avatar: [:export, :thumb]} }
    assert_equal expected_hash, Paperclip.missing_attachments_styles

    ActiveRecord::Base.connection.create_table :books, force: true
    class ::Book < ActiveRecord::Base
      has_attached_file :cover, styles: {small: 'x100', large: '1000x1000>'}
      has_attached_file :sample, styles: {thumb: 'x100'}
    end

    expected_hash = {
      Dummy: {avatar: [:export, :thumb]},
      Book: {sample: [:thumb], cover: [:large, :small]}
    }
    assert_equal expected_hash, Paperclip.missing_attachments_styles
    Paperclip.save_current_attachments_styles!
    assert_equal Hash.new, Paperclip.missing_attachments_styles
  end

  it "is able to calculate differences when a new attachment is added to a model" do
    rebuild_model styles: {croppable: '600x600>', big: '1000x1000>'}
    Paperclip.save_current_attachments_styles!

    class ::Dummy
      has_attached_file :photo, styles: {small: 'x100', large: '1000x1000>'}
    end

    expected_hash = {
      Dummy: {photo: [:large, :small]}
    }
    assert_equal expected_hash, Paperclip.missing_attachments_styles
    Paperclip.save_current_attachments_styles!
    assert_equal Hash.new, Paperclip.missing_attachments_styles
  end

  # It's impossible to build styles hash without loading from database whole bunch of records
  it "skips lambda-styles" do
    rebuild_model styles: lambda{ |attachment| attachment.instance.other == 'a' ? {thumb: "50x50#"} : {large: "400x400"} }
    assert_equal Hash.new, Paperclip.send(:current_attachments_styles)
  end
end