Have bash script answer interactive prompts

If you only have Y to send :

$> yes Y |./your_script

If you only have N to send :

$> yes N |./your_script

A simple

echo "Y Y N N Y N Y Y N" | ./your_script

This allow you to pass any sequence of "Y" or "N" to your script.

This is not "auto-completion", this is automation. One common tool for these things is called Expect.

You might also get away with just piping input from yes.