If you want to test bonus part you can easly extend this shell script for this purpose.

1. Clone it near your pipex directory

git clone https://github.com/HEADLIGHTER/pipexfasttest.git

2. Change PIPEXPATH in pipextest.sh to yours path to pipex

cd pipexfasttest && vim pipextest.sh

3. (optional) Write your own tests!
4. run pipextest.sh

./pipextest.sh

5. You are the best!