   # protractor config links _public/data to the test fixture data
   # directory.
   TEST_VOL_NBR = 20
+  # A Sarcoma001 Session01 volume number for which a test fixture scan
+  # image file is missing.
+  MISSING_TEST_VOL_NBR = 1
 
   page = null
 

        # button ElementFinders.
        download: elt.element(By.css('.glyphicon-download'))
        open: elt.element(By.css('.glyphicon-eye-open'))

  # Loads the image by clicking the given download button.
  #

          # The open button should be displayed.
          expect(open.isDisplayed(), 'The open button is hidden after download')
            .to.eventually.be.true

    it 'should display an alert box', ->
      # Find the download/display button pair, then...
      #
      # Work around the anomaly described in the scanImageButtons function.
      #page.scanImageButtons(MISSING_TEST_VOL_NBR).then (btnGroup) ->
        btnGroup = page.scanImageButtons(MISSING_TEST_VOL_NBR)
        download = btnGroup.download

        # Click the download button, wait for the image to load, then...
        page.loadScanImage(download).then ->
          # The download button should now be hidden.
          expect(download.isDisplayed(), 'The download button is displayed after download')
            .to.eventually.be.false
          # The unclickable exclamation sign button should be displayed after load failure.
          expect(failed.isDisplayed(), 'The exclamation sign icon is hidden after download failed')
            .to.eventually.be.true
