Add basic test case for `UploadRecovery`.

lib/upload_recovery.rb

@@ -47,6 +47,8 @@ class UploadRecovery
   end
 
   def recover_from_local(post:, sha1:)
+    return unless sha1.present?
+
     public_path = Rails.root.join("public")
 
     @paths ||= begin

spec/lib/upload_recovery_spec.rb

@@ -0,0 +1,48 @@
+require 'rails_helper'
+require_dependency "upload_recovery"
+
+RSpec.describe UploadRecovery do
+  let(:user) { Fabricate(:user) }
+
+  let(:upload) do
+    UploadCreator.new(
+      file_from_fixtures("logo.png"),
+      "logo.png"
+    ).create_for(user.id)
+  end
+
+  let(:post) do
+    Fabricate(:post,
+      raw: "![logo.png](#{upload.short_url})",
+      user: user
+    ).link_post_uploads
+  end
+
+  before do
+    SiteSetting.queue_jobs = false
+  end
+
+  describe '#recover' do
+    it 'should recover the upload' do
+      begin
+        stub_request(:get, "http://test.localhost#{upload.url}")
+          .to_return(status: 200)
+
+        expect do
+          upload.destroy!
+        end.to change { post.reload.uploads.count }.from(1).to(0)
+
+        expect do
+          UploadRecovery.new.recover
+        end.to change { post.reload.uploads.count }.from(0).to(1)
+      ensure
+        public_path = "#{Discourse.store.public_dir}#{upload.url}"
+
+        [
+          public_path,
+          public_path.sub("uploads", "uploads/tombstone")
+        ].each { |path| File.delete(path) if File.exists?(path) }
+      end
+    end
+  end
+end