Add a foreign-key constraint to the attachments table for blobs

activestorage/db/migrate/20170806125915_create_active_storage_tables.rb

@@ -20,6 +20,7 @@ class CreateActiveStorageTables < ActiveRecord::Migration[5.2]
       t.datetime :created_at, null: false
 
       t.index [ :record_type, :record_id, :name, :blob_id ], name: "index_active_storage_attachments_uniqueness", unique: true
+      t.foreign_key :active_storage_blobs, column: :blob_id
     end
   end
 end

activestorage/test/models/attached/many_test.rb

@@ -10,7 +10,7 @@ class ActiveStorage::ManyAttachedTest < ActiveSupport::TestCase
     @user = User.create!(name: "Josh")
   end
 
-  teardown { ActiveStorage::Blob.all.each(&:purge) }
+  teardown { ActiveStorage::Blob.all.each(&:delete) }
 
   test "attaching existing blobs to an existing record" do
     @user.highlights.attach create_blob(filename: "funky.jpg"), create_blob(filename: "town.jpg")

activestorage/test/models/attached/one_test.rb

@@ -10,7 +10,7 @@ class ActiveStorage::OneAttachedTest < ActiveSupport::TestCase
     @user = User.create!(name: "Josh")
   end
 
-  teardown { ActiveStorage::Blob.all.each(&:purge) }
+  teardown { ActiveStorage::Blob.all.each(&:delete) }
 
   test "attaching an existing blob to an existing record" do
     @user.avatar.attach create_blob(filename: "funky.jpg")