# File test/tc_screen_dumps.rb, line 16
  def save_screendump_for_file(url,filename)
    test_image=@@filecache.get_file_system_image(url)
    test_file=test_image.files[filename]
    assert_not_nil(test_file,"#{filename} should exist in #{url}")
    assert(test_file.respond_to?(:to_screendump),"#{filename} [class #{test_file.class}] does not implement to_screendump")
#    assert_not_equal(0,test_file.screendump_width)
#    assert_not_equal(0,test_file.screendump_height)
    save_screendump(test_file.to_screendump)
  end