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Testing URL Generator Implementation in Paperclip

This test suite evaluates the URL generation functionality in Paperclip’s UrlGenerator class. It validates URL construction for file attachments, handling of default URLs, and various URL formatting options including timestamp handling and character escaping.

Test Coverage Overview

The test suite provides comprehensive coverage of URL generation scenarios in Paperclip.

Key areas tested include:

Custom interpolator integration
Default URL handling for unassigned files
Lambda-based dynamic URL generation
URL character escaping and formatting
Timestamp appendage logic

Implementation Analysis

The tests utilize RSpec’s behavior-driven development approach with mock objects for isolation. The implementation employs MockInterpolator and MockAttachment classes to simulate file attachment scenarios and URL generation behaviors.

Notable patterns include dependency injection for interpolators and extensive use of mock objects for controlled testing environments.

Technical Details

Testing tools and configuration:

RSpec testing framework
Custom mock objects (MockInterpolator, MockAttachment)
Assertion-based validation
Spec helper integration
Isolated test cases for specific URL generation features

Best Practices Demonstrated

The test suite exemplifies several testing best practices:

Isolated test cases with clear, specific assertions
Comprehensive edge case coverage
Mock object usage for controlled testing
Descriptive test naming conventions
Modular test organization

thoughtbot/paperclip

spec/paperclip/url_generator_spec.rb

            
require 'spec_helper'

describe Paperclip::UrlGenerator do
  it "uses the given interpolator" do
    expected = "the expected result"
    mock_interpolator = MockInterpolator.new(result: expected)
    mock_attachment = MockAttachment.new(interpolator: mock_interpolator)

    url_generator = Paperclip::UrlGenerator.new(mock_attachment)
    result = url_generator.for(:style_name, {})

    assert_equal expected, result
    assert mock_interpolator.has_interpolated_attachment?(mock_attachment)
    assert mock_interpolator.has_interpolated_style_name?(:style_name)
  end

  it "uses the default URL when no file is assigned" do
    mock_interpolator = MockInterpolator.new
    default_url = "the default url"
    options = { interpolator: mock_interpolator, default_url: default_url }
    mock_attachment = MockAttachment.new(options)

    url_generator = Paperclip::UrlGenerator.new(mock_attachment)
    url_generator.for(:style_name, {})

    assert mock_interpolator.has_interpolated_pattern?(default_url),
      "expected the interpolator to be passed #{default_url.inspect} but it wasn't"
  end

  it "executes the default URL lambda when no file is assigned" do
    mock_interpolator = MockInterpolator.new
    default_url = lambda {|attachment| "the #{attachment.class.name} default url" }
    options = { interpolator: mock_interpolator, default_url: default_url}
    mock_attachment = MockAttachment.new(options)

    url_generator = Paperclip::UrlGenerator.new(mock_attachment)
    url_generator.for(:style_name, {})

    assert mock_interpolator.has_interpolated_pattern?("the MockAttachment default url"),
      %{expected the interpolator to be passed "the MockAttachment default url", but it wasn't}
  end

  it "executes the method named by the symbol as the default URL when no file is assigned" do
    mock_model = FakeModel.new
    default_url = :to_s
    mock_interpolator = MockInterpolator.new
    options = {
      interpolator: mock_interpolator,
      default_url: default_url,
      model: mock_model,
    }
    mock_attachment = MockAttachment.new(options)

    url_generator = Paperclip::UrlGenerator.new(mock_attachment)
    url_generator.for(:style_name, {})

    assert mock_interpolator.has_interpolated_pattern?(mock_model.to_s),
      %{expected the interpolator to be passed #{mock_model.to_s}, but it wasn't}
  end

  it "URL-escapes spaces if asked to" do
    expected = "the expected result"
    mock_interpolator = MockInterpolator.new(result: expected)
    options = { interpolator: mock_interpolator }
    mock_attachment = MockAttachment.new(options)
    url_generator = Paperclip::UrlGenerator.new(mock_attachment)

    result = url_generator.for(:style_name, {escape: true})

    assert_equal "the%20expected%20result", result
  end

  it "escapes the result of the interpolator using a method on the object, if asked to escape" do
    expected = Class.new do
      def escape
        "the escaped result"
      end
    end.new
    mock_interpolator = MockInterpolator.new(result: expected)
    options = { interpolator: mock_interpolator }
    mock_attachment = MockAttachment.new(options)
    url_generator = Paperclip::UrlGenerator.new(mock_attachment)

    result = url_generator.for(:style_name, {escape: true})

    assert_equal "the escaped result", result
  end

  it "leaves spaces unescaped as asked to" do
    expected = "the expected result"
    mock_interpolator = MockInterpolator.new(result: expected)
    options = { interpolator: mock_interpolator }
    mock_attachment = MockAttachment.new(options)
    url_generator = Paperclip::UrlGenerator.new(mock_attachment)

    result = url_generator.for(:style_name, {escape: false})

    assert_equal "the expected result", result
  end

  it "defaults to leaving spaces unescaped" do
    expected = "the expected result"
    mock_interpolator = MockInterpolator.new(result: expected)
    options = { interpolator: mock_interpolator }
    mock_attachment = MockAttachment.new(options)
    url_generator = Paperclip::UrlGenerator.new(mock_attachment)

    result = url_generator.for(:style_name, {})

    assert_equal "the expected result", result
  end

  it "produces URLs without the updated_at value when the object does not respond to updated_at" do
    expected = "the expected result"
    mock_interpolator = MockInterpolator.new(result: expected)
    options = { interpolator: mock_interpolator, responds_to_updated_at: false }
    mock_attachment = MockAttachment.new(options)
    url_generator = Paperclip::UrlGenerator.new(mock_attachment)

    result = url_generator.for(:style_name, {timestamp: true})

    assert_equal expected, result
  end

  it "produces URLs without the updated_at value when the updated_at value is nil" do
    expected = "the expected result"
    mock_interpolator = MockInterpolator.new(result: expected)
    options = {
      responds_to_updated_at: true,
      updated_at: nil,
      interpolator: mock_interpolator,
    }
    mock_attachment = MockAttachment.new(options)
    url_generator = Paperclip::UrlGenerator.new(mock_attachment)

    result = url_generator.for(:style_name, {timestamp: true})

    assert_equal expected, result
  end

  it "produces URLs with the updated_at when it exists" do
    expected = "the expected result"
    updated_at = 1231231234
    mock_interpolator = MockInterpolator.new(result: expected)
    options = { interpolator: mock_interpolator, updated_at: updated_at }
    mock_attachment = MockAttachment.new(options)
    url_generator = Paperclip::UrlGenerator.new(mock_attachment)

    result = url_generator.for(:style_name, {timestamp: true})

    assert_equal "#{expected}?#{updated_at}", result
  end

  it "produces URLs with the updated_at when it exists, separated with a & if a ? follow by = already exists" do
    expected = "the?expected=result"
    updated_at = 1231231234
    mock_interpolator = MockInterpolator.new(result: expected)
    options = { interpolator: mock_interpolator, updated_at: updated_at }
    mock_attachment = MockAttachment.new(options)
    url_generator = Paperclip::UrlGenerator.new(mock_attachment)

    result = url_generator.for(:style_name, {timestamp: true})

    assert_equal "#{expected}&#{updated_at}", result
  end

  it "produces URLs without the updated_at when told to do as much" do
    expected = "the expected result"
    updated_at = 1231231234
    mock_interpolator = MockInterpolator.new(result: expected)
    options = { interpolator: mock_interpolator, updated_at: updated_at }
    mock_attachment = MockAttachment.new(options)
    url_generator = Paperclip::UrlGenerator.new(mock_attachment)

    result = url_generator.for(:style_name, {timestamp: false})

    assert_equal expected, result
  end

  it "produces the correct URL when the instance has a file name" do
    expected = "the expected result"
    mock_interpolator = MockInterpolator.new
    options = {
      interpolator: mock_interpolator,
      url: expected,
      original_filename: "exists",
    }
    mock_attachment = MockAttachment.new(options)

    url_generator = Paperclip::UrlGenerator.new(mock_attachment)
    url_generator.for(:style_name, {})

    assert mock_interpolator.has_interpolated_pattern?(expected),
      "expected the interpolator to be passed #{expected.inspect} but it wasn't"
  end

  describe "should be able to escape (, ), [, and ]." do
    def generate(expected, updated_at=nil)
      mock_interpolator = MockInterpolator.new(result: expected)
      options = { interpolator: mock_interpolator, updated_at: updated_at }
      mock_attachment = MockAttachment.new(options)
      url_generator = Paperclip::UrlGenerator.new(mock_attachment)
      def url_generator.respond_to(params)
        false if params == :escape
      end
      url_generator.for(:style_name, {escape: true, timestamp: !!updated_at})
    end

    it "not timestamp" do
      expected = "the(expected)result[]"
      assert_equal "the%28expected%29result%5B%5D", generate(expected)
    end

    it "timestamp" do
      expected = "the(expected)result[]"
      updated_at = 1231231234
      assert_equal "the%28expected%29result%5B%5D?#{updated_at}",
        generate(expected, updated_at)
    end
  end
end