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Testing FileAdapter Implementation in Paperclip

This test suite validates the FileAdapter functionality in Paperclip, focusing on file handling, content type detection, and filename processing. The tests ensure proper handling of various file types, content type determination, and filename sanitization for secure file operations.

Test Coverage Overview

The test suite provides comprehensive coverage of Paperclip’s FileAdapter functionality:

File content handling and binary mode operations
Content type detection and validation
Filename processing and sanitization
File size and fingerprint generation
Edge cases including empty files and restricted characters

Implementation Analysis

The testing approach utilizes RSpec’s context-based structure for organized test scenarios. It implements before/after hooks for proper resource management and employs stubbing for MIME type detection. The tests validate both standard operations and edge cases using fixture files and temporary file handling.

Technical Details

RSpec testing framework with context blocks
MIME::Types for content type detection
Digest::MD5 for file fingerprinting
StringIO and Tempfile for file handling
Fixture files for test data

Best Practices Demonstrated

The test suite exemplifies several testing best practices:

Proper resource cleanup using after blocks
Isolated test contexts for different scenarios
Comprehensive edge case coverage
Mock and stub usage for external dependencies
Clear test organization and naming

thoughtbot/paperclip

spec/paperclip/io_adapters/file_adapter_spec.rb

            
require 'spec_helper'

describe Paperclip::FileAdapter do
  context "a new instance" do
    context "with normal file" do
      before do
        @file = File.new(fixture_file("5k.png"))
        @file.binmode
      end

      after do
        @file.close
        @subject.close if @subject
      end

      context 'doing normal things' do
        before do
          @subject = Paperclip.io_adapters.for(@file, hash_digest: Digest::MD5)
        end

        it 'uses the original filename to generate the tempfile' do
          assert @subject.path.ends_with?(".png")
        end

        it "gets the right filename" do
          assert_equal "5k.png", @subject.original_filename
        end

        it "forces binmode on tempfile" do
          assert @subject.instance_variable_get("@tempfile").binmode?
        end

        it "gets the content type" do
          assert_equal "image/png", @subject.content_type
        end

        it "returns content type as a string" do
          expect(@subject.content_type).to be_a String
        end

        it "gets the file's size" do
          assert_equal 4456, @subject.size
        end

        it "returns false for a call to nil?" do
          assert ! @subject.nil?
        end

        it "generates a MD5 hash of the contents" do
          expected = Digest::MD5.file(@file.path).to_s
          assert_equal expected, @subject.fingerprint
        end

        it "reads the contents of the file" do
          expected = @file.read
          assert expected.length > 0
          assert_equal expected, @subject.read
        end
      end

      context "file with multiple possible content type" do
        before do
          MIME::Types.stubs(:type_for).returns([MIME::Type.new('image/x-png'), MIME::Type.new('image/png')])
          @subject = Paperclip.io_adapters.for(@file, hash_digest: Digest::MD5)
        end

        it "prefers officially registered mime type" do
          assert_equal "image/png", @subject.content_type
        end

        it "returns content type as a string" do
          expect(@subject.content_type).to be_a String
        end
      end

      context "file with content type derived from file contents on *nix" do
        before do
          MIME::Types.stubs(:type_for).returns([])
          Paperclip.stubs(:run).returns("application/vnd.ms-office
")
          Paperclip::ContentTypeDetector.any_instance
            .stubs(:type_from_mime_magic).returns("application/vnd.ms-office")

          @subject = Paperclip.io_adapters.for(@file)
        end

        it "returns content type without newline character" do
          assert_equal "application/vnd.ms-office", @subject.content_type
        end
      end
    end

    context "filename with restricted characters" do
      before do
        @file = File.open(fixture_file("animated.gif")) do |file|
          StringIO.new(file.read)
        end
        @file.stubs(:original_filename).returns('image:restricted.gif')
        @subject = Paperclip.io_adapters.for(@file)
      end

      after do
        @file.close
        @subject.close
      end

      it "does not generate filenames that include restricted characters" do
        assert_equal 'image_restricted.gif', @subject.original_filename
      end

      it "does not generate paths that include restricted characters" do
        expect(@subject.path).to_not match(/:/)
      end
    end

    context "empty file" do
      before do
        @file = Tempfile.new("file_adapter_test")
        @subject = Paperclip.io_adapters.for(@file)
      end

      after do
        @file.close
        @subject.close
      end

      it "provides correct mime-type" do
        assert_match %r{.*/x-empty}, @subject.content_type
      end
    end
  end
end