Add spec DownloadsHelper to support testing csv downloads with headless chrome

spec/support/downloads_helper.rb

@@ -0,0 +1,38 @@
+module DownloadsHelper
+  TIMEOUT = 10
+  PATH    = Rails.root.join("tmp", "downloads")
+
+  def downloaded_filename
+    wait_for_download
+    downloaded_filenames.first
+  end
+
+  def downloaded_content
+    wait_for_download
+    File.read(downloaded_filename)
+  end
+
+  def clear_downloads
+    FileUtils.rm_f(downloaded_filenames)
+  end
+
+  private
+
+  def downloaded_filenames
+    Dir[PATH.join("*")]
+  end
+
+  def wait_for_download
+    Timeout.timeout(TIMEOUT) do
+      sleep 0.1 until downloaded?
+    end
+  end
+
+  def downloaded?
+    !downloading? && downloaded_filenames.any?
+  end
+
+  def downloading?
+    downloaded_filenames.grep(/\.crdownload$/).any?
+  end
+end