tests: move test/helpers to test/test_helpers.

The Rails convention is for test/helpers to be used for testing the view
helpers in app/helpers. We were using it to store certain utility
methods instead. Move these to test/test_helpers so that test/helpers
can be used for its intended purpose.

test/test_helpers/upload_test_helper.rb

@@ -0,0 +1,23 @@
+module UploadTestHelper
+  def upload_file(path, content_type, filename)
+    tempfile = Tempfile.new(filename)
+    FileUtils.copy_file(path, tempfile.path)
+
+    (class << tempfile; self; end).class_eval do
+      alias local_path path
+      define_method(:tempfile) {self}
+      define_method(:original_filename) {filename}
+      define_method(:content_type) {content_type}
+    end
+
+    tempfile
+  end
+
+  def upload_jpeg(path)
+    upload_file(path, "image/jpeg", File.basename(path))
+  end
+
+  def upload_zip(path)
+    upload_file(path, "application/zip", File.basename(path))
+  end
+end