Add additional checksum verification in specs

This adds an additional checksum verification to
the external files conversion spec. This ensures
that the FixityService returns the sha1 we expect
for the world.png file.

It also ensures that the checksums are the same
when the existing file is placed in `/tmp` and
that the file that is downloaded from a redirect
also has the correct checksum.

spec/services/external_files_conversion_spec.rb

@@ -2,6 +2,7 @@
 
 require 'rails_helper'
 require 'fileutils'
+require 'digest'
 
 describe ExternalFilesConversion do
   context 'running a conversion from internal to external file storage' do
@@ -10,22 +11,39 @@
     let(:user) { create(:user) }
     let(:work) { create(:public_work_with_png, depositor: user.login) }
     let(:file_set) { work.file_sets.first }
-    let(:filepath) { File.join(fixture_path, 'world.png') }
+    let(:filepath) { File.join(fixture_path, 'test.pdf') }
+    let(:fedora_sha1) { 'urn:sha1:ad13c5e7cc6d8198f25e003bd2965b3544e52a32' }
+    let(:fedora_sha1_without_urn) { 'ad13c5e7cc6d8198f25e003bd2965b3544e52a32' }
+    let(:sha1) { Digest::SHA1.new }
 
     before do
       allow(CharacterizeJob).to receive(:perform_later)
     end
 
-    it 'converts all works of a given Class' do
+    it 'converts all works of a given Class and has the correct checksums' do
       ENV['REPOSITORY_EXTERNAL_FILES'] = 'false'
       file_set
       response = Net::HTTP.get_response(URI(file_set.files.first.uri.to_s))
       expect(response.to_s).to match(/OK/)
       ENV['REPOSITORY_EXTERNAL_FILES'] = 'true'
       full_conversion
       response = Net::HTTP.get_response(URI(file_set.files.first.uri.to_s))
-      expect(response['content-disposition']).to match(/world.png/)
-      expect(file_set.original_file.original_name).to eq('world.png')
+      expect(response['content-disposition']).to match(/test.pdf/)
+      expect(file_set.original_file.original_name).to eq('test.pdf')
+
+      # Test the fixity service checksum
+      fs = ActiveFedora::FixityService.new(file_set.files.first.uri)
+      expect(fs.expected_message_digest).to eq(fedora_sha1)
+
+      # Check the checksum of the temp file
+      latest_file_directory = Dir.entries(Rails.root.join('tmp', 'external_internal_conversion')).sort.last
+      world_png = Rails.root.join('tmp', 'external_internal_conversion', latest_file_directory, 'test.pdf')
+      world_png_file = File.read(world_png)
+      expect(sha1.hexdigest(File.read(world_png_file))).to eq(fedora_sha1_without_urn)
+      world_png_file.close
+
+      # Check the checksum of the redirect repository file
+      expect(sha1.hexdigest(open(response.uri).read)).to eq(fedora_sha1_without_urn)
       expect(response.to_s).to match(/HTTPTemporaryRedirect/)
     end
     it 'converts a single work of a given Class' do
@@ -36,8 +54,8 @@
       ENV['REPOSITORY_EXTERNAL_FILES'] = 'true'
       single_work_conversion
       response = Net::HTTP.get_response(URI(file_set.files.first.uri.to_s))
-      expect(response['content-disposition']).to match(/world.png/)
-      expect(file_set.original_file.original_name).to eq('world.png')
+      expect(response['content-disposition']).to match(/test.pdf/)
+      expect(file_set.original_file.original_name).to eq('test.pdf')
       expect(response.to_s).to match(/HTTPTemporaryRedirect/)
     end
     context 'running from a file' do
@@ -69,8 +87,8 @@
         ENV['REPOSITORY_EXTERNAL_FILES'] = 'true'
         described_class.new(GenericWork).convert(file: pidfile)
         response = Net::HTTP.get_response(URI(file_set1.files.first.uri.to_s))
-        expect(response['content-disposition']).to match(/world.png/)
-        expect(file_set1.original_file.original_name).to eq('world.png')
+        expect(response['content-disposition']).to match(/test.pdf/)
+        expect(file_set1.original_file.original_name).to eq('test.pdf')
         expect(response.to_s).to match(/HTTPTemporaryRedirect/)
       end
       it "adds any ids it can't convert to an error file" do