How do I create a text image with a transparent value for the text with image magick

Question

I am using the following command to create an image of text with a shadow. What I would like to do is to create the text with a transparent opacity.

system('convert -background transparent ' .
      '-fill rgb(127, 127, 127) ' .
      '-pointsize 30 ' .
      'label:"This is a test" ' .
      '-background transparent -flatten -trim +repage ' .
      $fileName);

how would I go about modifying this to accomplish getting transparent text?